I drove a regular Is300 for a bit. It is in no way can compare to an regular 3 series. The cabin is small, no rear leg room, ride isn't nearly as good as bimmer, car doesn't feel planted to the road as bimmer, and don't even talk about the handling.
I'd like to say that isf cannot touch m3. C63 makes more sense if u want torque and it offers a nice cabin too.
So hell no!