I ran Asym2s on my old 135i, and I've got Supersports on my M135i.
Not exactly the same car, but both powerful RWD and according to the Internet, 99% likely to kill me as soon as it start spitting rain.
Supersports have better sidewall stiffness, so better 'feel'. They're say 10% more stable and grippy, but there isn't a 'night and day' difference.
Wet grip, I'd say they were the same. After 8k miles, the rears are 1/2 worn, the fronts 1/3 worn.