I'd have to disagree with you guys and actually ... can't believe I'm saying this .... agree with the 5th grear team.
If you want to scream round a track, the M3 is the clear winner. If I wanted a track day only car, I'd probably but an M3 (or perhaps an evo). However, as VBH hints at the end, for real world use, tescos, M6 and an occassional drag off the line, the softer, more comfortable and more user friendly C63 beats the M3 hands down.