It all depends on how often your roads are snow covered. I've done the 4 snows and the 2 in front definitely make a difference when you want to turn in the snow.

I put 2 Nokian's on my 94 e320 Wagon last year. Great in the snow but lousy on dry turns. I got a quick reminder this year in skid control from the back end breaking away. We get minimal snow here and the road crews do a reasonably quick clean up, so I need the snows primarly for unplowed street parking and snow drifts across the road. Michlein Alpines have best dry road handling per TireRack, so I'm putting them on my daughter's Scorpio.

Bob