Heavy-hitting performance and high levels of luxury meet in this pair of stately sedans.
In the red corner, we have the new Audi S6 quattro and its new 2.9-litre twin-turbo V6, while in the very dark blue corner sits the bulkier, brawnier 4.4-litre twin-turbo V8 champion of the autobahn, the BMW M550i xDrive.
Hang on, boxing match? No, no, no. That’s not right. This contest is as much about wits as it is about brawn. Maybe even more so.
Both are large luxury sedans capable of turning scandalous acceleration sprints with pointed handling. Both are every bit as luxurious as they are fast. The sad reality, though, is that most will spend more time creeping along clogged city streets on their way to meetings than they will on cross-continental grand-touring blasts.
That’s a shame.
Be that as it may, these high-level executive sedans (with muscle to flex under their conservative exteriors) have many a point to prove from the boardroom to a winding beachside road.
Pricing and Spec
Wouldn't you know it, but just a few days after I handed the keys back to BMW, the company announced a new, facelifted version of the M550i for Australia. You’ll have to forgive us for using the runout model.
That’s okay, though. For the most part, the changes are largely cosmetic. At its core, the M550i will remain much the same as the model seen here.
That means a starting price of $134,900 for the M550i Pure tested here, or $149,900 plus on-road costs for the full-fat model (simply called the M550i) that adds some extra bells to go with the already long list of whistles.
Both those prices will rise by $3000 for the updated model as it arrives.
Audi’s S6 is priced almost bang-on for the up-spec version from $149,536 before on-road costs. As far as close match-ups go, they don’t get much closer – or do they? Unlike BMW’s two-pronged approach, there’s just one variant of the S6.
The unmissable difference lives under the bonnet, where BMW’s twin-turbo V8 out-muscles Audi’s twin-turbo V6 – more info below in Drivelines.
BMW has good form in this area, too, pulling the same trick with its X5 M50i SUV that outperforms the Mercedes-AMG GLE53.
In developmental terms, the BMW is the older of the two, just. The current G30-generation 5 Series first went into production in 2016 compared to the C8 Audi A6 line-up that debuted in 2018.
That’s nitpicking a little, but shows in differences with infotainment tech, interior decor, and some of the available technology.
In terms of basics, both come as four-door sedans only. Inside, they share key features like a digital instrument cluster, colour head-up display, power-adjusted front sports seats, keyless entry and ignition, powered boot lid, leather seat trim, adaptive cruise control, auto lights and wipers, adaptive cruise control, and quite a lot more.
By stepping up from BMW’s Pure version, you add extras like laser headlights and soft-close doors, active anti-roll stabilisation and rear-wheel steering, a leather-trimmed dash, a sunroof, and metallic paint – although the latter two have been options on this particular car.
Audi has an optional Dynamic Package available as an answer to the non-Pure mechanical upgrades from BMW. It’s not fitted here, but adds variable-ratio steering, four-wheel steer, and a quattro sport rear differential. It’s a $7700 ask on top, if you’re keen.
Pricing, while not exactly cheap, is still decent value. These are clearly very advanced and very luxurious sedans. They’re big and certainly spacious.
If you line them up against something like an Audi RS5 or Benz C63, roughly cross-shoppable on price, it gets tricky to justify the more focused and hi-po alternatives. All the more so when you consider how few opportunities there are to really exploit all that performance on Aussie roads.
That said, splitting the win for this round is tricky. As a more modern-styled package with imposing performance and considerable specs, the S6 is easy to love, but the old-fashioned muscle offered by the M550i, without any significant back step in equipment, makes round one a draw.
We'd better delve further, then.
|BMW M550i xDrive||Audi S6 Quattro|
|Colour||Mediterranean blue metallic||Tango red metallic|
|Options as tested||$5000||$1700|
|Servicing – 3 years||$1850, prepaid||$2350, prepaid|
|Warranty||3yr/unlimited km||3yr/unlimited km|
Tech and Infotainment
BMW may well have been the frontrunner when it came to infotainment tech when it first introduced the iDrive system on the 7 Series in 2001. Audi didn’t lag far behind, though, answering with the somewhat similar MMI control interface for 2002’s A8.
In the two decades since, both systems have been overhauled, expanded, and are almost completely different today.
BMW sticks with its rotary controller, but now also adds shortcut buttons, finger-tracing letter entry, voice commands, touchscreen operation and optional gesture control.
Audi ditched the clickwheel for this generation, and runs with talk and touch input methods, using an additional screen for handwriting recognition, and making the most of pinch and swipe gestures with haptic feedback in the same way a phone or tablet does.
As a result, BMW maintains physical buttons for climate controls and places the iDrive controller further back, while Audi does more things with its all-screen climate controls that can jump in for other functions.
In terms of real estate, the BMW runs a 12.3-inch display high up in the centre of the dash. Audi uses a slightly smaller 10.1-inch display, and below that an 8.6-inch secondary screen.
Both use a 12.3-inch digital instrument display, but whereas Audi will let you choose from a selection of display options including mapping, BMW locks the display. You can choose some trip computer functions, but the display format is locked, and instead of maps BMW uses a small stylised greyscale line diagram that leaves a lot to be desired when it comes to ease of use.
Audi and BMW will let you wirelessly connect your smartphone for Apple CarPlay mirroring, but right now only Audi allows (wired) Android Auto use, though BMW promises Android compatibility is coming soon.
Both come with 16-speaker branded audio systems – Harman Kardon for BMW and Bang & Olufsen for Audi. BMW doesn’t offer any audio upgrades, but Audi has a 1820W 19-speaker B&O Advanced 3D sound package (again, not fitted here) that is exquisite to listen to, with an equally exquisite $11,700 price.
So, which is the better system? Rather annoyingly, it’s hard to pick them apart. They’re very closely matched. Just, and only just, Audi’s menu layout is a little simpler to work through as you deep-dive into functions. Load times between pages feel snappier, too.
The press-to-click interface is an odd experience at first (like force-touch on an iPhone or Apple Watch), but soon makes sense and becomes natural.
BMW has dropped the ball with a more complex arrangement. The interface is still simple and pleasant to use, but some functions are buried too deeply, and there’s a small lag that would be barely noticeable were it not for Audi’s crispness.
Wireless phone pairing never hiccuped once in the Audi, but could take longer to connect in the BMW, though we were never locked out the way iDrive has done on some BMWs in the past.
By the slimmest of margins, Audi gets this round.
Before any comparison is made, Audi’s raw-finished carbon twill option (at $1700) deserves a special mention. It’s truly stunning in person – technical and tactile all at once.
Glossy carbon is old hat these days. Sadly, BMW’s plasticky “fine-wood” is even older hat alongside.
Back to cabin basics, though, and there are a couple of standout points.
BMW has a better driver’s seat. It feels more supportive, hugs a little better without feeling too tight, and seems to have the right balance of thigh and lumbar support.
On the other hand, the S6 seats look much more sporty. If the M550i treads a traditional path, the Audi’s fixed head restraints and quilted inserts are the modern sporty alternative.
Unfortunately, the bums-on-seats test reveals a flatter, broader-feeling seat that lets you slip, just a little, from side to side as you pick up the pace. There’s still plenty of adjustability, but not quite the same long-range support.
In the rear, the difference may come down to personal taste. I feel like the M550i’s seat base is too long for my sawn-off legs, and the Audi is a better fit.
On the other hand, the Audi lacks the knee and toe room for long-distance travel, and all the more so with taller adult occupants. Getting into the Audi’s taller door aperture is easier, though, and jumping between the two saw me clash my head in the BMW more than once… Experience counts.
Both cars feature rear air vents and four-zone climate control, so rear passengers can tailor comfort to suit. Audi will let you add rear sunshades as an option, while BMW reserves this upgrade for the non-Pure (or should that be impure?) M550i.
Front seat passengers will find more physical controls at their fingertips in the BMW, which leads to another important detail: fingerprints.
Because the screens are the primary input method in the S6, the interior clouds up with fingermarks much more quickly. Perhaps it's my own neuroses, but in the M550i I tended to use the other control methods more and kept the interior cleaner as a result.
Good news, there’s a microfibre towel in the glovebox of the S6. It’ll get a hearty workout if you buy one, I’m sure.
The quicker and easier access to more functions in the BMW makes it a little easier to learn and get used to. If you’re likely to often swap cars with your other half, you’ll spend less time hovering a finger looking for controls in the M550i.
Boot capacity is a matching 530L for both, though there appears to be a surprising amount of wasted space behind the panelling on the sides of each. BMW frees up a little extra width in the rearmost section, making it easier to squeeze in a set of golf clubs or two, but gets narrower as you head towards the front of the boot.
How’s this for a curious detail? The S6 doesn’t use physically connected door-release handles. From inside the cabin, the release is electronically controlled to tie in with the system that protects you from opening the door into an oncoming cyclist or car.
As a result, there’s a small delay between pulling the door and having it open. Audi says you won't notice, but once you do it becomes a strange obsession. Opening the BMW’s door is fluid and natural. Tension builds behind the handle, the release pops, and you push the door.
Audi’s door handle feels flimsy and disconnected. There’s no pressure and then the door just swings away from you. Call me a stickler, but Audi needs to go back to the drawing board on this one. It erases so much of the premium feel found elsewhere.
How to call this one, then? The superior spaciousness of the 5 Series or the improved rear-seat access of the S6? Perhaps the ease of operation for BMW’s controls, or the technical slickness of Audi’s presentation?
Dare I penalise Audi for its misguided door-release experience? I won’t. There’s a richness to BMW’s interior with better seats and better seat space that gives it the win for this round.
|BMW M550i xDrive||Audi S6 Quattro|
|Wheels/tyres, front||20x8.0-inch 245/35 R20||21x8.5-inch 255/35 R21|
|Wheels/tyres, rear||20x9.0-inch 275/35 R20||21x8.5-inch 255/35 R21|
From a 2.9-litre V6, Audi delivers 331kW between 5700 and 6700rpm, but most of the heavy lifting is done by 600Nm of peak torque available from 1900 to 5000rpm.
Conversely, BMW draws 390kW at 6000rpm and 750Nm from 1800 to 4600rpm from a 4.4-litre V8.
Both engines are twin-turbocharged, and both send power to all-wheel-drive systems via eight-speed automatic transmissions.
Points to BMW, then. No doubt about it, but hang on, Audi says the S6 has a thirst for 8.4 litres per 100km of fuel, while BMW says 10.6L/100km.
A slightly disjointed test regime meant it wasn’t possible to pull perfect back-to-back figures, but a few snapshot glimpses of the trip computers showed the Audi to run in the high 12s after some urban and spirited running, while the BMW showed low 12s in the same conditions.
That’s perhaps not enough to set the two apart, but Audi is further from its claim and working harder to deliver the same kind of performance.
On a purely emotional front, both deliver satisfying engine noises, and befitting their positioning as refined and subtle sports cars, there’s never any boisterous overshare of exhaust noise.
BMW’s V8 sounds, well, like a V8. It’s burbly and well rounded, but also quite faint. The Audi has a higher pitch, and sounds excitingly technical, plus the augmented sound as you cycle through driving modes makes it more prominent inside the cabin.
There’s a very limited range where you can get the Audi to grunt on upshifts; a more measured version of the burble found in more pointed Audi Sport models. The M550i doesn’t do that, it just shifts note from deep to deeper as it picks up its next gear.
Crucially, though, against the stopwatch there’s daylight between the two. BMW says the M550i will hit 100km/h in an impressive 3.8 seconds. The Audi is still quick but more sedate at 4.5 seconds.
Put it all together and it’s easy to find a favourite. The Audi S6 is certainly impressive, but the more muscular BMW M550i snares the win.
|BMW M550i xDrive||Audi S6 quattro|
|Engine configuration||V8 twin-turbo petrol||V6 twin-turbo petrol|
|Displacement||4.4L (4395cc)||2.9L (2894cc)|
|Power||390kW at 6000rpm||331kW @ 5700-6700rpm|
|Torque||750Nm at 1800-1600rpm||600Nm @ 1900-5000rpm|
|Drive||All-wheel drive||All-wheel drive|
|Transmission||8-speed automatic||8-speed automatic|
|Fuel consumption (combined cycle)||10.6L/100km||8.4L/100km|
On the Road
Hit the road and these two cars neatly fall into distinct categories. One caters to the driver’s whims, the other pampers as a grand tourer – but a fast one, nonetheless.
With air suspension underneath, there’s a waftiness to the S6. It does a better job of blotting out ragged road surfaces, and even in the firmer Dynamic setting it has a firm but supple balance for erasing dips and fractures in the tarmac.
The S6 also feels light-footed; it dances more delicately through bends with lighter steering. There’s less feedback through the wheel. The steering accurately points the front wheels, but the driver is almost completely isolated from feel or feedback.
With its wider spread of torque, it’s easier to find on-tap urge within the Audi’s reserves, but with less sheer get up and go, it can feel like you need to push deeper into those reserves to keep pace with the M550i.
Grip and balance are never issues. Audi’s all-wheel-drive expertise shines with balanced front to rear traction. There’s no pronounced sense of drive scrambling from end to end. The big Audi simply holds on tight, although it can slip into controlled but noticeable understeer if a road switched from flowing to more technical.
Conversely, the BMW has a greater feeling and connection with the road.
The suspension, while still adaptive, isn’t air-sprung, and while it never verges into uncomfortable, the ride channels more of what’s happening under foot into the cabin. The result isn’t unpleasant, and whereas the S6 can occasionally give a rising stomach sensation on rollercoaster roads, the M550i can feel more buttoned down.
There’s more weight to the steering and more feedback. It doesn’t quite match the Audi’s sharp front-end reactions, but the more intimate relationship with the road paints a better picture for the driver.
While it may proudly wear an xDrive badge on its rump, the M550i has no issues with behaving like a rear-wheel-drive car. In more dynamic driving, the front end is more faithful, but the rear is prepared to tug playfully at the limits. It won’t step out wildly, but it lets you know who’s boss – then torque shifts to the front wheels, and you can feel the balance shift as the front tyres take some of the load off the busy rears.
Rolling acceleration is just a heartbeat away in the BMW, and two or three beats later the Audi hits its stride. The extra kilowatts of the M550i make themselves known in press-on situations, resulting in a more enticing dynamic drive.
As for more relaxed travel, the BMW is smooth and quiet at a freeway lope; the Audi is smooth and quieter. Not by much, as both are impressive, but it’s easier to relax on an extended drive in the Audi.
Both offer impressively capable adaptive cruise control and lane-centring systems for extra peace of mind on cross-country trips.
In town, the S6 is the more alert of the pair. It’s much easier to find the Audi’s get up and go. Disappointingly, the M550i feels rather dull at urban speeds.
It lacks the torque down low for a brisk low-speed amble. This comes as a surprise when the same engine in an X5 M50i feels brawny and capable. Something in the sedan version's calibration feels a little off.
Familiarity is key here. At first, the M550i didn’t inspire confidence for jumping into fast-flowing traffic, but it is never slow – you just need to know how to load the accelerator to tap into what’s available.
In a perfect world, you’d have the S6 for commuting, and you’d probably give it the nod for a long-haul driving holiday. The M550i is the car you roll out on weekends searching for coastal roads and challenging mountain passes.
Because of its more impressive feel and feedback, and the siren’s call of great driving roads, the BMW just edges out its competitor here.
It is incredibly disappointing to think that you can shell out more than $150K on one of these cars and only get a three-year warranty.
There’s no distance cap, and brand representatives will insist that owners don’t get left out in the cold should something untoward happen, but relying on Australian Consumer Law or goodwill warranty extension is much like having to prove your innocence.
Prestige brands claim to have superior engineering, so perhaps it's time to match that with a warranty that is at least the equal of $20,000–$30,000 mainstream cars. For reference, Lexus provides four years' warranty, Mercedes-Benz offers five years, as does newcomer Genesis.
Prepaid service plans are available from both brands. A three-year service package for the S6 costs $2350, while the M550i is a little more affordable at $1850.
While the BMW may be cheaper in this instance, there are no winners in the warranty stakes.
On category wins, BMW takes this one. Audi doesn’t lose, though, and you could be well served by either car.
The magic mix really would be the Audi’s slick interior and restrained crisp styling with BMW’s beating heart and handling. Oddly enough, the previous S6 came with a V8 – the new car is superior to the old one, but the engine not so much.
The sensible part of me recognises that the S6 excels as a daily driver, but if that were enough, an A6 55 TFSI could do the same at a $33K saving. Still a turbocharged V6, still with all-wheel drive, still competent, but not as focused on outright dynamics.
Head lower in BMW’s range, and one rung below the M550i there’s only the four-cylinder 530i. No dice. The M550i is an irreplaceable treat within the 5 Series range.
With Audi, Mercedes-Benz, Jaguar and Lexus all retreating from the V8 game, at the sub-flagship level, BMW offers a unique proposition in the marketplace.
More power, greater driver involvement, and better passenger accommodation are just icing on the cake, really.