I have found that my summer tires, Michlin XGT-H4s provide good dry and wet traction (much better wet traction than BFG Comp TAHR4), but also wear quite fast.
My last set of winter tires, Michlin Arctic Alpins (235-75 R15) lasted very well (guessing over 100K km, I'm too lazy to look up where I changed over every fall and spring); they provided very good ice and snow traction for the first 4 winters, but were not as grippy last winter. Though they weren't down to the wear bars, I have just replaced them with 4 Michlin Latitude X-ice (235-70 R15) tires on the car. The Arctic Alpin is a new style of snow tires, and seem to work better floating over deep snow than the older styled ones did digging through it, so maybe going to a 70 series isn't so bad a change. I will let you know how the new snows work out.
Studs provide the best traction on ice, but if you try going 100mph with them the studs will come out.
If I lived in the mountains I would have a set of chains in the luggage compartment for the beast. Nothing beats chains in deep snow, but unless you have a beater you only use on snow-days, you don't want to have them on your car all the time. They will wreck your tires, you cannot drive at any reasonably efficient speed with them on, and they are a bit of a pain to put on and take off.