How well they work in winter depends not just on brand but at least as much on how the particular unit is equipped. Enclosed heated tanks, plumbing within the heated envelope of the RV, dual pane windows, etc. all play a real part in how cold you can comfortably operate.
I have enclosed/heated tanks (via the furnace) and plumbing inside my class C, but not double-pane windows. I've done limited camping/overnighting down in the 20's without it being problematic. It does get a bit drafty inside, and the furnace can consume a fair bit of battery power if dry camping. Dump facilities are even rarer at that time of year around here, and they're none to plentiful at any time.
If you're in an area where they salt the roads, it might be wise to take into consideration the extra corrosion that can bring. Thorough washing/hosing off of the underside with clean water fairly soon after traveling is a wise idea to help limit salt damage. The basic chassis framework and components are not usually the main concern here; rather, the angle irons and so forth that the RV maker uses to construct the RV are usually more prone to damage by corrosion (plus any exposed systems/electrical connections).
My class C handles fine in the snow, based on pretty limited experience. There's plenty of weight over the rear wheels for traction. I try to avoid anything much in the way of winter weather; I don't care to find out how it would behave if things got really dicey and it started to actually get away from me, and can't imagine it would necessarily end well.