Mercedes-AMG C63 S Coupé vs BMW M4 Competition Pack - twin test

We can thank its rival from Munich (and, more distantly, the one from Ingolstadt, too) for that. The profit-making badging conceit of BMW and Audi has clearly signalled to Mercedes that the C-Class Coupé needs a distinctive ‘look’ to go with its two fewer doors and, to its credit, its amalgamation of newly blistered arches and a Mercedes-AMG GT-inspired tail is enormously eye-catching – enormous enough, in fact, for the normally standout M4 to slip into its shadow for the morning. And considering the sparkle of its standard 20in M Star wheels and the gold of its very much optional calipers beyond, that’s quite a feat.

The C63 probably edges it inside as well. From the door card Burmester stereo speakers to the IWC clock to the fist-sized three-ring vents, the cabin glints like an architect’s pencil case. Not all the lustre is eye-pleasing (it’s predominantly the shine of plastic posing as metal), but the net effect dips nicely under the bling radar – even with the swathe of optional carbonfibre on the console.

The M4 – as familiar inside by now as an old leather jacket – is far more buttoned down. It smells like a leather jacket, too (preferable to the synthetic non-scent of Mercedes’ man-made trim material) and probably features the better brace of plush sports seats. Its unequivocal twofold advantage sits between them: on top, the iDrive multimedia display – far superior to its rival’s Comand system – and down below, in the four inches of flick-happy gear selector adjacent to your left hand.

The bulbous stick is nothing tremendously special, but because AMG has unwisely (or, more likely, necessarily) stuck with its parent firm’s god-awful column shifter, it suddenly satisfies the palm like a one-handed catch at leg slip. The C63 is not without its advantages, of course – most notably, the panoramic sunroof that comes as part of the £2595 Premium Pack. Why so? Because the carbonfibre roof on the M4 negates having one there, and a hole in the ceiling is useful when you want to hear what’s going on outside.

The fiddly photography done, we need to saunter slowly north and then dogleg west on the M4 motorway to latch onto the B-roads of Wales’ underpopulated interior. First up, the C63. The S gets essentially the same hand-assembled twinturbo 4.0-litre V8 as the standard model, meaning it’s a wet-sumped close relative of the GT’s engine – which makes its symphony of forged aluminium and zirconium alloy about as cutting edge as a  big-capacity petrol motor gets. Its latest output is prolific: 503bhp and 516lb ft of torque, which is more peak twist than even the GT S has.

This shows. The starter C63 (also 37lb ft back) is exceedingly keen. The S is something else. After a cough and a bark, it settles into a background pulse, simmering like a prison yard moments before a riot breaks out. Engage drive, though, and the creep is molasses. There’s a giant, bandy, supple leg somewhere in the multi-plate MCT that engages its clutches with the sympathy of Hoke Colburn, letting the C63 S sweep majestically forward on the crest of a rising sound wave.

The gentleness and Mariana Trench depth of this unhurried progress will be familiar to big-displacement fans – but its sheer from-idle tractability (clearly although not conspicuously aided by the blowers spinning up between the cylinder banks) is exemplary. In implied profundity, it is unchallenged by the M4. The Competition Pack delivers more outright power than the regular model, but its torque delivery is unchanged at 406lb ft.

Plainly, a 110lb ft deficit is noticeable, although BMW doesn’t help itself with a more fraught throttle response from its snappier pedal, and with less fuel in the cylinders to work with, the straight six is manifestly more dependent on its turbos hitting their stride. To label the 3.0-litre unit as languid would be ridiculous, given the energy with which it will eventually commit to turning its carbonfibre driveshaft. But against the background of the V8’s supreme flexibility, its performance is less appreciably three-dimensional – a characteristic that extends to the motorway, where neither its Efficiency mode nor its Sport setting succeeds in replicating the sonorous, smooth-shifting part-throttle thrust of the C63.

However, the M4’s forte is just as readily appreciable around the paucity of its engine note. In the cabin and running gear, the BMW is significantly quieter than the Mercedes. The C63’s shortfall in isolation we’ve identified before – and the S, on wider, lower-profile tyres, does not enhance the situation. It extends to the ride quality, which, although fine on the long-wave undulations of the M4 motorway, is frequently undone by the endlessly changeable, occasionally cliff-faced obstructions of rural Welsh roads.

Truthfully, its moderate brittleness would be easier to dismiss if it weren’t highlighted by the extraordinarily adept level of wheel control BMW has brought to the Competition Pack. Hardware changes, particularly in the damping, have lent the previously abrupt M4 a genuine deftness over broken asphalt. In Comfort mode, it lives up to the description marvellously, as does the steering, which has a lighter, crisper edge to it than the slightly muddy feel of the C63’s laziest setting.

All of this makes the BMW marginally more convenient to spend oodles of time in, even without the V8’s broader capacity for driver captivation. Better still is the chassis’s ability to absorb much more vigorous inputs within the same congenial bubble of refinement. As the roads get quicker, so does the M4, its colossal grip, wonderful balance and the assuredness of its lane placement popping up in the consciousness instantly and with unforced intuitiveness. The quality of the car’s  contact with the road is the predictable secret; ditto the weight of the controls used to keep it there.

The C63, concurrent with its less consistent dynamic, speeds up faster but without necessarily ensuring the same sure-fire level of confidence. This has less to do with putting its power down (something both cars do admirably well) and more to do with responsiveness, the larger, heavier AMG feeling marginally less swift to turn in and less adroit in its body control thereafter. The sensation of a slightly higher roll centre and the C63’s habit of being unsettled more easily than the M4 makes it sit atop the road rather than knee deep in it. At seven-tenths, on the ascent into our chosen valley, the Competition Pack’s shrewd enhancements leave just the right kind of impression.

By the time Luc Lacey breaks out the camera gear again, the weather has closed in. Where there ought to be green, there is now a lingering squall of battleship grey and sufficient water in the atmosphere to dampen the spirits of a whaleboat captain. Not the sort of conditions you’d necessarily choose for sampling inordinately powerful rear-drive coupés away from a skidpan, but his nibs, head to toe in Goretex, waves play on from the non-existent safety of a verge regardless.

Predictability and assertiveness are the standard requirements now, and as the preference for sure-footedness gives way to a more belligerent adjustment of cornering attitude, the innate playfulness of AMG’s chassis tuning pops up like laser sights on a water pistol.

For M division, the Competition Pack’s directive has apparently (and not unreasonably) come with the stipulation that it must be quicker around a track. As such, the active M differential, anti-roll bars and fatter tyres are evidently more committed to the task of keeping you straight, which is commendable and results-driven, but it does make traction loss that bit trickier to manage when it eventually occurs – especially when the spikiness of the engine’s delivery is taken into account.

In the C63 S, all concerns are immediately allayed by the knowing inclusiveness of its gargling, tyre-wrecking back end. The merest hint of a bung will have the electronically controlled diff (as opposed to the mechanical one on the standard C63) embracing a slide with the co-operative benevolence of a beanbag. Its control thereafter never seems in question, thanks to the speed and weight of the steering (suddenly clarified by the selection of Race mode) and the supremely linear response of the V8 at practically any revs.

It’s one-dimensional perhaps to claim victory for the AMG on account of this single-corner showing – but understanding its accessibility over the limit (something it will heartily prove even with the traction control positioned at its half-mast Sport setting) has the quintessential effect of enlivening the driver experience across the board. The M4, for all its new-found suppleness and usability, is ultimately hard-nosed by comparison, encouraging you to lean into its mammoth limit but disinclined to pay off with anything other than more speed without a circuit-based level of commitment.

Frankly, in a £60k-plus coupé that’s unlikely ever to see a track day, I prefer AMG’s concept of driver reward – particularly as it’s embellished at the opposite end of the scale with a soundtrack and stride pattern as expansive as the one belonging to the rakish V8 and a physical allure unmatched by anything not branded with a Jaguar or Porsche trademark. Neither attribute entirely erases the patchiness in between, and I’ll admit to savouring the Competition Pack’s roundedness on the long drive home. But it’s the irrepressible C63 S that’s now squirrelled away in the fun-time memory banks – and firmly atop our most-wanted list.

Mercedes-AMG C63 S Coupé

Rating 4.5/5; Price £68,080; 0-62mph 3.9sec; Top speed 155mph; Economy 32.8mpg (combined); CO2 emissions 200g/km; Kerb weight 1800kg; Engine layout V8, 3982cc, twin-turbo, petrol; Installation Front, longitudinal, RWD; Power 503bhp at 5500rpm; Torque 516lb ft at 1750rpm; Power to weight 279bhp per tonne; Specific output 126bhp per litre; Compression ratio 10.5:1; Gearbox 7-spd MCT automatic