I really couldn't tell that much of a difference between my 35i M Performance and a 50i M Sport I had as a loaner in the speed department, it didn't feel that much faster. It didn't have adaptive drive which probably contributed to the front end feeling heavy and it certainly didn't sound better. I'd like to try a 50i M Performance with AD because I bet it sounds and feels much different.
15 BMW 328d xDrive Sports Wagon M Sport
15 Audi SQ5 Prestige
13 Honda Insight EX