heres how the current m5 does against the rs6
and have u ever herd of the bugatti veyron, the fastest car in the world? its awd, i love my e30 but awd doesnt spin it sticks, it doesnt go sideways in corners and you have more traction in every situation u could possibly think of. i live in canada where awd is key for a year round yuppie car, my old man has had m6's m5's 540's 740's m3's and the best everyday car he has every bought as much as it hurts to say is the s6 he just got before the winter, he has the m3 for fun in the summer but that s6 rocks as a year round cruiser and in our last trip out east around xmas it was unbelieveable. Im sure the 740 he used to have would have been ok but there nothing like that awd confidence.
If your talking track car id prefer rwd personally but its hard to argue when u see the bugatti go up against the zonda.