Tests have shown that all season tires aren't any better than highway tires. The rubber's too hard to grip in snow and the tread doesn't do much either. The recommendation was to use good highway tires for longevity and if you have snow, put on real snow tires.
I believe that many winter wrecks are caused by people thinking their all seasons are snow tires. They aren't.
Yup! If you have real winter driving conditions, forget all seasons and get some real winter tires. For occasional use, get two sets of chains.
We've gone through several sets of Bridgestone Blizzaks, a set or two of Hankooks and I'm currently on a set of Nokian
Hakkapeliittas, pretty sure my wife's car is on Blizzaks. On most of the cars we've run them year round. Yes, I know you're not supposed to, but our winter driving conditions are over 1/2 the year and our summer temperatures are fairly mild. We get three years out of a set of winter tires, vs. six years for a set of summer and winter tires, and don't need an extra set of rims.
I haven't seen a huge difference in grip between the various brands. The one brand I'd suggest avoiding is the Hankooks as they seem to have the most tender sidewalls. You don't have to hit a pothole very hard to get a bulged sidewall.