Coming from a 2007 MCS
I just wanted to add my opinion on the whole hot hatch thing. I recently (6/12) bought a 2010 e90 M3 and just drove my 2007 MCS with Alta tune for the first time in a month. In June I was also driving around my bro's Mazadaspeed3.
Driving at semi-legal speeds the MCS is more fun to throw around. It definitely is less refined and accelerates slower than the M3. I can't wait to take the M3 to the track sometime. The MCS also has more road feel. My previous 03 330i zhp had even more road feel.
The Mazda has too much of an on off effect with the turbos and clutch engagement was way too soft. It's handling is good but road feel sucks.
I guess I will have to take the M3 to the track to get the full experience. Public roads is too dangerous and scary for the M3!