Studs won't help in snow, but sure help you on ice. I've ridden in winter without them, but it's much nicer to have studs, especially with all the melt/freeze cycles we tend to see in my area (and yours seems similar). Studs don't help you in snow--you need an aggressive lugged tread pattern for that. Slush and snow that have been tracked around by cars are a nightmare no matter what kind of tires you have, at least in my experience.

Schwalbe and Nokian brand studded tires have carbide studs, which will last quite a long time even if you ride on a lot of bare pavement. A lot of other brands have studs made of hardened steel, and they tend to wear down more quickly.

The best description of some of the higher-quality tires is here, with a pretty good selection guide: http://www.peterwhitecycles.com/studdedtires.asp

For what you describe, I'd be looking at the Nokian W106, or the Schwalbe Marathon Winter. The Nokian apparently has a more aggressive tread, performs better in snow, and has higher rolling resistance. I have a set of 40 mm Marathon Winters that I've been pretty happy with so far this year, but there hasn't been tons of deep snow (apparently, I live too far to the north!)