First, I have total respect for Audi products. My dream car is the R8 v10 right now. I would take that over any other car if I have that money to spend (yes even over a Ferrari, Lambo, etc).
I also come from a long history with Audis, having owned or driven many of their cars in the last 15 years including the Coupe Quattro, A4s, S4s, S6s, S8s, A6 4.2, RS4, RS6, TT, and R8 (only the V8 version).
I live in the Northeast, where we do get snow and all sorts of crappy weather.
I only started buying the BMW brand, but I must say that I would prefer the drive of BMW's rear-wheel drive, sport driven cars, over Audi's right now. Even in the snow (with a good set of winter tires). To me, the drive-ability/sportness of BMWs are just better then Audi right now. After driving Quattro for many years, I totally dig the rear-wheel drive aspects of cars like the M3.
So while the RS5 is still a great car, and lets be honest, its one hot-looking car, - it will never surpass the M3 but maybe match it in certain criteria. For the M3 to do so well against a new model is a great testament to BMW, no matter how you try to spin the 'which car is better argument'.
Now if BMW can only build a R8 fighter.....