I ended up going with the Michelin Pilot Exalto A/S this year, and they're doing about as well as you can expect a RWD LSD car to do in severe blizzard type snow, I guess. I haven't gotten stuck in two inches of packed snow yet or anything, at least. I got stuck a few times last year in ridiculous amounts of snow, with the PZero Neros M&S. They sucked! Never again. I can't imagine they're good in either mud or snow. Pirelli lied!
I love getting sideways, as long as I don't get stuck.
Still, I wouldn't even try to drive it in anything over about 5 inches of snow. 6 inches and the car stays home. It just piles up under neath it too badly.