I've ridden through 30+ winters and used studded tires less than 5 times. I have a studded tire that I've owned for 3 years for that I've used those less than 5 times. For the other 27 (roughly) years through blizzards, ice storms, snow packed roads, unplowed trails, etc., a mountain bike with aggressive off-road knobby tires (and some skill) has done just fine. I have crashed a few times but not excessively. Nor have my crashes been excessively severe. Studded tires are nice but not totally necessary. Skill is far more important and the only way to develop skill is by doing.

I also have to disagree with you, dskyer, on the effects of crashing on a large person vs a smaller person. Yes, the physics say that the force of impact are greater but there are other factors to consider in how a human can mitigate and redirect those forces. We are much more than just lumps of meat. I've learned through years of experience how to fall so that I don't get hurt or don't get hurt badly. Even a smaller person who doesn't know how to fall correctly can get seriously hurt. Again, it's a skill that needs to be developed by doing...unfortunately.