Yeah I have considered it an option. I expect both cars to perform similar. The RS4 is such a strong performer that its showing up in comparisons with the M5.
However, I would rather own an M3. For me it comes down to price. If the M3 is cheaper than the RS4, which it should be, then I will probably go with the M3. If the price is a lot higher than I am expecting then the RS4 becomes an alternate....