I prefer a wider (2") studded tire in most snow conditions, since I won't be "cutting down to the pavement" in snow that has been previously traversed by tractor-trailers.

When the snow is slushy and not too deep (common urban scenario), a narrow tire will displace it and usually grip the salted underlying pavement just fine.

But in such conditions I use narrow slicks (28c) for decreased rolling resistance, not because they actually give me better traction.