Beneath the skin of the RS5 lie some rather more senior alterations and a serious amount of technological hardware. Motive power comes from a 4.2-litre V8 that's closely related to both the V8 and V10 engines used in the Audi R8 supercar.
It makes its maximum output – an impressive and M3-eclipsing 444bhp – just 100rpm shy of its 8300rpm redline, yet peak torque comes in as low as 4000rpm, so it promises to be fast and flexible. It's the first Audi RS model to put its drive through a seven-speed, dual-clutch gearbox.
For the purposes of this test, so closely aligned are the two rivals that we also took along a Competition Pack-equipped M3 to the RS5's performance testing session.
The RS5's launch control and four-wheel drive traction enables it to hit 30mph in a belting 1.8sec (BMW 1.9), but it is an advantage it cannot hold even to 60mph, which the Audi reaches in a very creditable 4.6sec. The thing is that the BMW is even quicker, with a 0-60mph time of 4.5sec. At 100mph (10.7sec in the Audi) the M3 holds a two-tenths advantage.
In truth, these are such small differences that they prove relatively unimportant, so let's not take anything away from the RS5, because it's a car with an exceptional drivetrain.
You'd swear it has more flexibility than the M3 at low to medium revs (although its 30-70mph time of 7.6sec in fourth is 0.6sec slower than the BMW's), and with an 8300rpm redline it has a tremendously broad spread of power, a cracking throttle response and a thrilling soundtrack.
Left to its own devices, the S-tronic gearbox is pretty smart, but there are also paddle shifters that allow full throttle without kickdown for richly baritone-accompanied acceleration, while shifts are barely perceptible in both automated and manual modes.