Originally Posted by Ed Holland
I will admit to using my wife's folding ATB when there is snow on the road - the road bike wouldn't stay upright for long in those conditions
I'm not sure if you speak from experience, but my experience disagrees with your statement. For 6 to 8 winters, I was a year-round cyclist in Alaska and in Montreal, Quebec. I never had a road bike until the last winter I was in montreal, but on snowy days in montreal the road bike was my bike of choice.
They never fail to salt the roads in center city Montreal. What that means for a bike with narrow (25mm or so in my case) tires is that the tires sink through the snow and the rubber rides on wet pavement. By contrast, on snowy days the mountain bike forced me to use lots of effort while the tires pushed snow out to the sides. The tires were less able to consistently sink through the snow, which meant the bike and i were bumping up and down over snow. Traction was fine for both bikes, though I think in a pinch the road bike would have come out better, because it was able to get more rubber down to the pavement.