I think studded snow is not legal in a lot of places in US/Canada, at least on pavement.
The problem with summer tires on the snow/cold is that their rubber is designed to work a much hotter temperature that they just don't grip as well since tires are designed to flex and the rubber supposed to create interlocking with the surface they are on. Generally dedicated winter snow tire is supposed to have much softer compound and different construction to deal with the cold, plus deeper/wider thread gaps to clear snow/water. Summer tire also tend to have cleaner, larger chunk of tread block for dry pavement to give it more grip, so snow/water won't clear as well and creating chances for skidding/hydroplaning. All season is just in between and works a bit for everything but good for nothing....They are good if you are cheap( like me for the 4 banger Camry that I drive), but they are really "good for no season". RS-As are annoying because they are supposed to be "high-performance all season" and is expensive, but I just find it to be poor in general. The Michelin you mentioned is more of a "dedicated" all season(its available in 215/55 R17?). Probably rides better than RS-A but as such not much grip in general. In my dad's case I usually advise him to change to snow past Oct/Nov just because it gets cold already.
University of Toronto Formula SAE Alumni 2003-2007
Formula Student Championship 2003, 2005, 2006
www.fsae.utoronto.ca