Have driven both M3 coupes and M3 sedans around VIR as fast as I could (BMW 2-day Advanced M-School ... and going back this Spring). If there's a difference between the two it's too subtle for this hacker to detect.
Now the comparo between the 'old' M3 and the new M5 (recently at Spartanburg) ... old M3 wins by a mile. Comng off lease on my 335i in 2015 is going to be fun. 335i? 4-series? M3? Life is sweet.