Great thread. The driver makes the biggest difference. But as with lights, knives, skis, and nearly everything else - having better equipment puts you in a better position to use your skills, and can oftentimes save your skin or help make a bad situation less bad.
When I lived in Colorado, I had dedicated studded snows. It was before Blizzak's - started with a "V", I think. Very highly regarded in the mid-'80's.
They would pull me through anything, but I learned very quickly that you need more than two!
Now, I live where it snows once every 16 years, and I only make it up to ski once or twice a year so dedicated snows just don't make sense for me.
I've taken extreme performance summer tires (Dunlop Sport 8000's) to Tahoe. With chains, they got me there okay. Without chains, a less-than-4% grade stopped me in my tracks.
In my old Jetta on Bridgestone high-perf all-seasons, I had no trouble on the grade or the bends while my buddy in his compact 4WD Toyota with mud tires was sliding around quite a bit.
Now that I'm a family man, I don't seem to need that last 5% of dry traction, so my wife and I have ExtremeContact DWS on my RWD Mercedes and her FWD Volvo. They are sticky, balanced, forgiving, quiet, comfy and amazing in the wet. I hope to find out how they do in the slippery stuff in a couple months. They blow our stock Michelins and Pirellis out of the water on ALL fronts. I've been very impressed with them, but in all honesty I'll probably get some summer tires for the Merc next time. Generally, if we're going to the snow, we'll take the wagon - which means FWD.