The best tyres on snow IMHO are all-terrains, really smooth road tyres aren't that great and full on mud-terrains aren't that great. I think the theory being that AT's have lots of sipes in the tread (=grippy edges) but whatever the theory the reality is quite noticeable. Road tyres without any siping e.g. Avon Rangers (the old type crossply, not what they sell as a "Ranger" now) or the Rangemaster, are truly deeply scary on snow and ice. A good mud terrain like a BFG is certainly better than something like a Rangemaster on ice (I have BFG MTs on the 110) but not nearly as sure footed as a good all terrain.
BFG ATs are good as are the General AT2s, for best effect (and assuming the road speeds allow it) drop a few psi out of the tyres for a bigger contact patch, it makes a noticeable difference in really bad weather but obviously you can't run them fast like that. Also beware of an inch or two of slush with any wide tyre as aquaplaning on slush suddenly becomes much more interesting