The Carrera is nice and it'd be a great drivers' car. I can say the same for the M3, but the S5 just captures bits and pieces of the high-points of both cars...and damn I just think it's one of the most beautiful cars ever built. That engine sounds better than both, I'd say, the interior is top of it's class, and it's got a rock-solid build.

The M3 is probably the better all-rounder...but in a matter of personal preference, I'd much rather have the S5. It's a bit more exclusive and certainly more of "my thing" than the other cars.