I would be surprised if F80 M3/4 isn't better than the B8 RS4/5 in terms of driving pleasure, after all, an front-engined AWB can never pull out a corner like a FR; and the nose-heavy Audi's have been criticised by its cabin-forward design as it hampers performance.
'sides, the current turbos are notorious for their massive torque in mid-range when pulling out of a corner. I secretly doubt any more than factory default will result in massive torque steer and kill the fun...
But let's wait and see how the new A4/5 fares when the it comes out later this year.
BTW, this is the 2nd Beemer that makes me really want to own one...