The grading of winter tyres goes roughly like this, from best to worst (in terms of not falling off):
Studs plus knobs - Schwalbe Ice Spiker
Studs - Schwalbe Marathon Winter
Special compound and tread pattern - Continental Top Contact Winter
Normal "winter" road bike tyres - Conti GP 4 Seasons
Ordinary tyres
The rating from slowest to fastest is pretty much the same too
Marathon Winter are noticeably hard work, enough so that I only fit mine when I expect lots of ice, rather than just the odd patch.
Studs alone don't give much grip in snow, but the problem then is more lack of progress than hurting yourself.
Top Contact Winter are quite a lot nicer to ride, and not noticeably slower than the average town & canal towpath 35c hybrid tyre.
I use these once regular frosts have started. I had them up to about 10% going directly uphill on sheet ice before they span out (by way of a testing ride).
GP 4 Seasons are a bit better than standard tyres, but they are aimed more at cold & damp rather than ice.
I've retired from regular winter club rides now, but they are what I used to use, and they were OK for 25 miles in the Cotswold hills for the average icy night (i.e. roads mostly dry), provided that you were alert and ready to slow right down for icy patches, or possible icy patches. If you are on ice (lack of tyre noise is a giveaway), or think you may be, don't turn or brake other than extremely gently, and don't do anything that's going to upset your balance, such as looking round when someone else falls off.
What you can't do with any tyre is to ride like you do when it's dry and warm enough that ice isn't a possibility.
