I’ve done a lot of winter cycling on icy roads on various tires, and I can’t emphasize enough what a difference studded tires make. Studded tires are the difference between dangerous and hesitant riding to confident cycling and maneuvering.
20 years ago, the only commercial option for winter cycling was expensive imports from Finland. Even today, Nokian tires like the Nokian Hakkapeliittaare favored by experienced winter cyclists, and these days are available for about the same price as similar tires from Continental and Schwalbe.
My only experience is on Nashbar studded tires, which are just re-badged studded tires from Kenda. They’re about 20% less expensive than Nokian, Conti and Schwalbe because they have fewer studs and use software steel. The softer steel wears down more quickly if you ride on a mix of clear pavement and ice conditions.
Fewer studs means a little less traction, but on mostly clear roads with patches of ice in shady areas, those low stud count tires work well. Higher stud count is helpful if you ride along frozen ruts. Think of the slush at an intersection that freezes overnight, and that’s what high stud count tires are made for.
Some studded tires have a very open tread, which are designed to bite into and shed snow. These tires are good for trail riding where you’ll encounter deep snow. For city riding where ice and slush is more typical, less aggressive tread might be better. If the roads and paths in your area are cleared and you only need to deal with the occasional icy patch, the least expensive tires with low stud count should be fine. Otherwise, the general purpose tires like Epon’s Schwalbe Marathon Winter are just about perfect.
Studded tires are available in “road” bike diameters as well as mountain bike 26″ sizes. The “700C” tires are very wide and will only fit on cyclocross bikes and 29″ mountain bikes. I think the narrowest I’ve ever seen is this Nokian Hakkapelitta 700×32, which is still too wide for a typical road bike.