1. The most dramatic difference would be seating position in the driver's seat, but other than that, if you can feel a difference in performance between the E90 m3 and E92 m3 (given same option, same stock wheels + tire), you should be a DTM race driver.
In fact, a well known test driver (Tsuchiya, aka drift king in Japan) who went through 30 yrs of Tsukuba circuit testing 5000 cars on Best Motoring Magazine, did a lap on the Tsukuba circuit (1.287 miles), on same equipped M3 coupe (Nav, CF roof, stock 18 inch, 6MT) and Sedan (Nav, No sunroof, stock 18 inch, 6MT), and the E90 sedan was 0.33 sec faster around the track than E92.
It says something, especially this guy who's more stable at track than any other race driver and the circuit was only 1.2 miles long...
2. E9X gen 6MT does not come with rev matching system, the only "electronic assist" MT has is hill assist.