Mowermech: eloquently put, as always.
One thing, maybe not obviously posted in your post, but there nevertheless, is the question of operator skill.
Experience driving in winter conditions is probably the most important part of anyone operating vehicles in the brutal, northern border winters.
Four wheel drive or two wheel drive, operator experience and driving to match road conditions, and NOT the posted speed limit, is above and beyond the most important factor.
That said, there are times, matched with horrible conditions, where four wheel drive and or snowmobiles are the only things moving. Operator skills can only get a person so far, then one reaches the performance limits of any machine.