I drive a torque happy RWD Chrysler 300C in all the snow central Ohio has thrown at me for the last two Winters and have had no problems (yet) on non snow tires. I head out to pick up my 01 RX 300 AWD tonight in DeWitt Iowa that I bought off of ebay.
I expect the "AWD" RX will be even better than the 300C and FWD Odyssey I have now. The 01 X5 was not great in the snow but better than any RWD Bimmer.
The Best AWD systems are Audi, Jeep, and Subaru. Newer BMW systems are better than original.