Numbers don’t lie. But they rarely tell the full truth either. Just look at the new Audi RS6 Avant which, numerically, is an absolutely bulletproof choice. Its 4.0-litre V8 generates 552bhp. Thanks to Quattro, aggressively spaced bottom gears, launch control and superglue rubber it can accelerate to 62mph in 3.9sec, accompanied by a whiff of tyre smoke and a faint trace of charger whine, yet the claimed fuel consumption is a remarkably frugal 28.8mpg.
In addition it has eight gears to the M5’s seven, has a cavernous 565-litre boot (45 litres more than the BMW), 21in wheels instead of 20s and 420mm front brakes where the M5 has 400s. If this was a points contest then it’s game over.
But consider this: the true test of a great driver’s car is not the amount of tech or power, but how those assets are deployed. Too much technology can get in the way, and both these cars are flirting with tech overload. Audi’s Drive Select system has evolved into hard work by encouraging the driver to programme an increasing variety of vehicle characteristics, including everything from damper settings to the pitch of the exhaust note. There are no less than five different driving modes to choose from: Comfort, Auto, Dynamic, Individual and Lift (the latter being specific to the air suspension). It would be quicker to start up an Airbus.
The BMW M5’s more like a 737. They’ve learned from the mistakes in the overly complex DNA of the previous V10-engined M5. You can still personalise engine/transmission, steering, shift speed, dampers and the stability programme, but the keys to do so are now grouped around the transmission lever, ready for action. Better still, you can programme two pre-set modes through a pair of steering-wheel buttons. So, you get airborne quicker.
The RS6 remains, in the true tradition of fast Audi estates, a blunt instrument to drive. Despite ceding 20bhp to its Lamborghini V10-engined predecessor it produces a massive 37lb ft of extra torque (516lb ft in all) which it smears onto the road in a fat, flat, juicy curve all the way to 5500rpm. Leave it in Auto and rely on the hugely flexible Quattro drivetrain – which can dish up to 70% of the torque to the front wheels or up to 85% to the rear – and you can simply hoon it like a hot hatch, not even worrying about understeer unless you suddenly change direction mid-corner. Switch to Manual and you’ll have to be constantly on the ball to stop the V8 crackling into the limiter through the first few cogs.
The tweakable steering works best left in Comfort – stick it in Dynamic and it weights up without any appreciable feel, plus there’s a vague spot as you turn into a quick corner.
The M5, though hefty by M Sport standards, is 65kg lighter than the RS6 (no Quattro gubbins, see?), yet it’s half a second slower to 62mph. With similar torque on tap at comparable revs, the difference is down to the extra traction and better gear ratios, but again the figures aren’t the whole story. The BMW’s steering is far superior, remaining haptically connected no matter how much lock you wind on, and its input/output ratio is both linear and immediate. Tip: don’t fiddle with the steering calibration options – they merely morph ‘perfect’ into ‘heavy’ into ‘very heavy’.
The M5 feels really quick in the mid-range, its steady torque complemented by proper dramatic punch as the revs rise, and the DCT dual-clutch seven-speed ’box outshines the Audi’s eight-speeder, albeit with less artillery drama than the previous M5. The BMW’s variable damper settings are better sorted, too, with Dynamic being less firm than the RS6’s and Comfort being less mushy. Audi may have gone too far off the scale at both ends.
Inside the cabins both cars make a decent fist of creating a bit of driver theatre – the M5’s head-up display features a rev counter that changes colour from amber to red as 7000rpm approaches, while the RS6 pulls the same stunt using LEDs that flash the cabin with, ahem, ‘upshift lightning’. Both cars are dark, cool and honed inside, the Audi’s honeycomb seats and milled controls being the more stylish, but the M5’s rubber-coated gear paddles stealing the honours for fingertip tactility.
But this test is not decided by cc, bhp, lb ft, mph, mpg, sec, litres or pounds sterling. Our preferred yardsticks are heart and head, in this order. The Audi is bi-turbo fast, Quattro-earthed and four-rings-solid. A future champ, no doubt, a highly competent attempt at perfection. But at the same time this is a strangely soulless automobile, remote and rather cold, chip-biased and not a particularly gifted communicator. Kind of a triumph of machine over man, really. The M5 is an extremely well balanced all-rounder, a master of feedback, honest through and through, always ambitious but never aloof. It is, by a short head, the better car.