Driving involves 3 main things, all of which become more difficult on ice/snow - Accelerating, turning, and braking.
Trucks and SUVs are at a disadvantage compared to cars because of their higher center of gravity and higher weights. The added weight and weight distribution make it harder to stop and turn, which seem to be the most important parts.
This may sound odd, but my AWD wagon (Volvo V70R) does waaay better than our Jeep Rubi in the snow and ice. It really isn't even close - those Swedes know how to build a car that is like a billygoat on ice and snow!
The Jeep does have 1 main advantage and that is toughness. In my old TJ, there were a number of times that I was stuck in stopped traffic because of a wreck ahead and I simply drove over a curb and median/ditch, to get to an access road. Sure wouldn't do that in the wagon.