I have two setups for real winter. One with a slightly aggressive (cyclocross) type tread pattern and a single row of studs. The other is pretty aggressive and heavily studded - Nokian/Suomi Extreme! The latter is good for roads with snowpack that turn to sludge and ice during the spring thaw. Handy in Wisconsisota
I made it through one Wisconsisota winter with just cyclocross tires, no studs. They sucked on anything remotely icy, including glazed snowpack. I had to stick to the salted main roads that winter. They were good for fresh snow without ice, though.
North Carolina, on the other hand...road race tires have been just great, except for the two days of ice. I use studs on that.