Hi everyone
I think the RWD is better overall than the FWD and the gap gets larger in snowy/slippery conditions. The problem with the front wheel drive in slippery conditions is that when going uphill, the weight of the car shifts toward the back and the pressure on the front tires ( due to the weight of the car ) becomes less, thus less traction on the front tires which makes it harder to move the car forward.
Watch this video for Fifth Gear, it's a very informative car shows.
http://www.youtube.com/watch?v=JcQaHhSMGKM