I have a set of 700x 35c studded tires. Early each winter, the road conditions get bad and I chicken out and install the studded tires. They are better on black ice but the rubber compound doesn't do so well when the temperature drops to -15c or colder and I end up slipping around. They also have a tendency not to shed warmer, wetter snow, bunging up the fender area causing great drag.

After the roads gather a little gravel, I switch over to 700x32 Ritchey Trail Mix tires and usually finish off the winter season no matter what mother nature throws at me, even conditions as bad as those that forced me to the studded tires. Great tires with an aggressive tread but easy to pedal.

I get about 200kms use on the studs to the 3000kms on the Trail Mix tires each winter. Its all how you ride I guess.