Of the three Ms we drove, I would get the M3. Fast, but not over-powered and that DCT is SCHWEET. The SMG in the M6 would kick you in the back if you shifted any where near redline (which we did with great abandon). It was neat that the M6 would rev-match as you downshifted. That car is an animal but a bit heavy.
For the hot lap ride with the instructors, they chose the M5. Gotta be a reason.