Tested: 2021 Audi RS7 vs. BMW M8 GC vs. Mercedes-AMG GT63 S

Elana Scherr
·12 min read
Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver

From the May 2021 issue of Car and Driver.

In response to the question "How do you make a 600-hp sports sedan?" Audi, BMW, and Mercedes-AMG have turned in answers so similar that if this were an exam, they'd be accused of cheating.

The brands started with the bones of a buttoned-down sedan and crafted a version with a narrow-eyed performance-car glare, a dropped roofline, and a sloping tail. Each car has all-wheel drive, adaptive dampers, brake rotors the size of Saturn's rings, and a twin-turbo V-8 of at least 4.0 liters making completely unbuttoned dyno numbers. Add up all three and you get 1838 horsepower.

Presumably to enrage our readers, the marketing people advertise these things as four-door coupes. "Swoopy, saggy-assed sedans" could work, but that doesn't quite capture the seriousness of this trio.

The Audi RS7, the BMW M8 Competition Gran Coupe, and the Mercedes-AMG GT63 S are heavyweights in price and performance. All have the sleepy menace of a tough guy no longer at his leanest but still packing a mean right hook. And left hook. And headbutt. They're just a launch-control start away from proving it.

Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver

The GT63 tops the list in both power and cost, with 630 horsepower and—prepare the smelling salts—a $204,260 as-tested price. Comparatively, the M8 seems like a horsepower-per-dollar bargain at an as-tested $167,245 for 617 ponies. The RS7 is our underdog, with 591 horses, but it's also the least expensive: Our Tango Red test car arrived nearly fully loaded for $137,540.

That there are even three choices of racy, sweptback quasi-sedans is astounding. It hints at some alternate universe where everyone lives on an Alpine mountain and commutes to an office at the top of another peak and between them is the Nürburgring Nordschleife. Oh, and they all carpool.

Living in that fantasy world and missing from this test is the 620-hp Porsche Panamera Turbo S. While it would have fit the budget, power requirements, and lozenge shape of the segment, Porsche didn't want the Panamera on this fight card and wouldn't cough up a car.

Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver

Perhaps it was because we were motoring around in Southern California rather than yodeling through the Alps and terrorizing the 'Ring, but our collective enthusiasm for these pricey four-doors was lacking. "Why am I not more excited about these cars?" testing director Dave VanderWerp asked, poking dispiritedly at the decorative exhaust tips on the AMG. He got no reply from tech editor David Beard, who was busy researching which Jelly Belly flavor the Designo Brilliant Blue Magno Mercedes resembles (Jewel Blueberry, if you're wondering).

Then we drove them: The revelation came not on the straightaways but through miles of twisty canyon, up and down mountains. When we stopped at an overlook, the mood had changed. We were no longer ambivalent. Someone breathed, "Effing magic," an echo to the tick, tick of parked-when-hot exhaust. We had forgiven the droopy behinds and linguistic marketing gymnastics, completely entranced by the family-size four-doors with the hearts of backstreet brawlers.

Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver

Third Place:
BMW M8 Competition Gran Coupe

Highs: Quick starts, quick stops, adolescently ferocious rear-wheel-drive setting.
Lows:
The ability to find and amplify every road imperfection, steering that hates its job.
Verdict:
An amazing car for escaping in a cloud of smoke, not so much for daily driving.

If this were a drag-racing competition, the M8, well, the M8 would still lose despite its ridiculously quick 2.7-second 60-mph time and 10.8-second quarter-mile. While those numbers would do a supercar proud, the GT63 is even quicker. And yet we're going to call the M8 the dragster of the group, because while the Benz and BMW can disable their all-wheel-drive systems to become rear-drivers, only the M8 will do a "Big Daddy" Don Garlits–style burnout. Though that feature might matter only to us and the fine folks at Tire Rack who are probably filling an order for $778 worth of replacement 285/35ZR-20 Michelin Pilot Sport 4S rear tires right now.

Judged solely by the testing equipment, the M8 wouldn't have finished last. Its all-out acceleration times beat the RS7's and were a mere tick behind the GT63's, and its 147-foot stop from 70 mph and 291-foot stop from 100 led the pack. The BMW's passing times and 5-to-60 acceleration beat the others', too, and it tied with the Audi for best as-tested fuel economy.

Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver

What hurt the M8's score was the way it generates those numbers. It ranked at the bottom in all the subjective dynamic categories. The undoing starts with steering that feels less interested in your needs than a DMV employee on a Friday afternoon. If a car could roll its eyes, the M8 would do so the second you put the steering in Sport mode ("Oh yeah, I'll get right on that"). The team also liked the BMW's brake feel least. Although the $8150 carbon-ceramic setup stops hard, the brake-by-wire system is nonlinear when the driver is trying to be gentle, and everyone agreed that having two brake settings (Comfort and Sport) is stupid.

There are so many settings that the settings have settings. To make it easy to quickly recall your favorite setup for steering effort, transmission aggression, brake feel, throttle response, stability control, and exhaust volume, BMW fits two programmable M modes. There are also three suspension modes, ranging from Comfort to Sport Plus.

Ah yes, comfort. It's lacking here. With a barely passing grade in the ride category, the Gran Coupe has earned the D that's missing from its name. The BMW has large front seats and good space in back for two, but the middle seat seems a bit optimistic since anyone sitting there has to straddle a console—it's like riding the world's worst mechanical bull.

Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver

As you'd expect from the $167,245 price, the car comes very well equipped. All three offer just about anything you'd expect from a luxury or performance model and scored evenly on features and amenities. Inside, there's a big shiny touchscreen, carbon-fiber trim, quilted leather, heated and ventilated front seats, a heated adjustable steering wheel, wireless Apple and Android connectivity, adaptive cruise control, a menu of driver's aids to keep you safe and sane, and a more expansive menu of the aforementioned performance-mode options for occasions when you want the opposite.

In motion and placed in its softest settings, the M8 jitters and sidesteps over uneven pavement. In the mountains, where you'd hope to see the benefits of the stiff suspension, the M8's handling seems reluctant for a car that'll circle the skidpad with 1.02 g's of cling. Although it's the lightest in the group, the M8 is the least fun, and fun is critical for a four-door sports car.

Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver

Second Place:
Mercedes-AMG GT63 S

Highs: Steering, braking, and engine roar exactly like the sports car it's named after.
Lows:
Rigid, clomping ride; passes the $200,000 mark.
Verdict:
A grand tourer that's plenty grand, just not when it comes to touring.

Talk about a comeback kid. At the start of this test, the blue jellybean was nobody's favorite. All of these cars have largish rear ends, but the GT63 would benefit most from some Spanx. It's the loudest of the group at 70 mph; the only thing you can say about the excessive wind rush is that you're unlikely to notice it over the even more excessive tire noise. Like the BMW, the AMG is unyielding even in its most gentle suspension setting. "Perhaps the C on the mode dial stands not for Comfort but for Chiropractor," quipped one of the Daves.

In testing, the loud tires—wide Michelin Pilot Sport Cup 2s, the most aggressive rubber here—earned the Merc points by holding on to the skidpad with 1.05 g's. The AMG punched a 2.6-second time to 60 and a 10.7-second quarter-mile with a 129-mph trap speed, knocking out the Audi and the BMW.

Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver

It's too bad every bump thicker than a painted lane marker ripples through the floor and seats, because the GT63's interior is visually and physically appealing. The heavily bolstered and pleated front $2500 AMG Perform­ance buckets make you feel like Venus on her half shell, if she had risen from the sea foam with reservations for a track day. Their low-mounted position adds to the racing feel, especially when the engine is revving and the exhaust is popping. There's a lot of theater here for sure. Although the GT63 is the only one in the group without a middle seat, its rear seats offer more room and support than the Audi's or the BMW's. AMG's goal appears to have been to implant the spirit of the two-door GT into something that could hold a couple of child seats. Mission accomplished.

Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver

Of the three cars in this test, the $204,260 GT63 S—the most expensive by a large margin—offered the most amusing options and details. Well, no, actually those rear-drive burnouts in the M8 were the most amusing, but the AMG did have a foldout shopping crate and a cutout in the cargo hold to store it. Surprisingly, even for all that dough, ours didn't have the perfume atomizer that fills your car with Benz-designed scents, but we weren't bothered. We likely would've shut it off anyway in order to smell the pepperoni-pizza-flavored Combos strewn about the cabin during vigorous cornering.

Plunging the Mercedes into turns made us forgive its lack of comfort. When the road turned wiggly squiggly, the GT63 hunkered down and cut right through. The steering and automatic transmission are so responsive, you may suspect they're reading your mind. All 4620 pounds of this car dissolve when the engine unleashes its full 630 horsepower and 664 pound-feet of torque. Confidence builds, adrenal glands pump, arm hairs quiver, serious driver face becomes gleeful grin. Who can hear road noise over their own heavy breathing? If the M8 wins at the drag-strip burnout box, the GT63 is the clear champion of the canyon road.

Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver

First Place:
Audi RS7 Sportback

Highs: Serene ride, still so fast, massive cargo space.
Lows:
The inability to brag about a sub-three-second 60-mph time, all the letters from readers who judge only on the numbers.
Verdict:
A tamed monster that gives up just the slightest edge of excitement in favor of usability.

At the test track, the RS7 couldn't break the three-second barrier to 60 mph or dip into the 10s in the quarter-mile. But if moving 4806 pounds from a dead stop to freeway speed in 3.0 seconds isn't quick enough for you, we'd like to live where you do.

The RS7 doesn't offer the manic attentiveness of the Benz or the caffeine-jag jitters of the BMW. Its ride, general demeanor, and automatic transmission are less edgy. Instead Audi lays on the luxury a little thicker. Not only are the 14-way leather seats the cushiest, but the ride is smoothest by a large margin. The combination of air springs and adaptive dampers erases the sins of paving crews like a medieval indulgence that actually works. All of this is great, except it also extends to the exhaust note; even with the $1000 sport exhaust, the RS7 was by far the quiet­est and least involving of the bunch.

Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver

If the grip levels aren't as high as the others' and the steering isn't quite as toasty-crisp as the AMG's, the difference isn't big enough to make you want to leave the RS7's cocoon of black leather and textured carbon fiber in pursuit of the harsher delights of its competitors. While its skidpad score of 0.98 g trails the pack, its sure-footed handling makes keeping up with the Bimmer and Benz easy, and the rear-wheel steering will help you through your missed apexes. Although the Audi came up short of the Mercedes in the fun-to-drive quotient, it is more engaging and satisfying to chuck down a great road than the BMW. Audi didn't forget about practical matters either. The RS7 buyer enjoys the largest cargo area, holding the most carry-on-sized boxes in the test.

Photo credit: Jessica Lynn Walker - Car and Driver
Photo credit: Jessica Lynn Walker - Car and Driver

Before you accuse us of growing as soft as the cars we're testing, remember that these are four-door sedans. You might have passengers—several passengers, children even. Being able to hit a crack in the road and describe the fine points of its edges may be desirable in a track car, or even a Sunday-only sports car, but a sports sedan shouldn't rob luxury to pay performance. Put another way, the RS7 is the only one of this stunningly quick bunch that won't wake a toddler on the drive home from Grandma's.

The Audi is the car we'd recommend to anyone shopping for one of these bolides. It balances sportiness and luxury better than the other two. It's a sweetheart when you want it to be, a gentle heavyweight you can introduce to your parents, but it also has the handling, acceleration, and joy of a sports car. The best part: It does it all for less money than the rest.

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