Having driven and raced on both a 215/45/17 and 205/55/16 version of the same winter tire, I can say that the differences were about what you'd expect.
The 215s had better grip on bare ice (wider contact patch), but the 205s definitely did better when driving through deep snow. In Chicago there were plenty of times I was driving through deep snow in the winter, I did it for fun. We had a blizzard 3 years ago on the day of the Super Bowl, I went driving for fun with a bunch of friends while everyone else waster their time watching football.
Neither tire felt necessarily great in dry/warmer weather, but handled just fine. Ride quality with the 205s felt better (and the 16s looked cooler). I really don't think you can argue much of a hard point either way. Get what suits you and your budget.
I'll be switching back to a 215/45/17 this year, but that's mainly because I want the wider contact patch for ice racing events. I'd run 15s if it wasn't such a PITA to find a set that works. haha
As long as you have winter tires, you're ahead of the game compared to a lot of the dumbasses that own these cars and try claiming they make it through winter just fine on their summer tires.
