I've had an assortment of good winter cars, but the worst would be a Mustang II Cobra I had in college. The summer performance tires just made it that much better. I remember replacing the heater fan in a parking lot one cold xmas.
I once tried my 911 in snow. Started it, put it in gear, got out and watched the wheels spinning at idle with absolutely no traction, got back in and shut it off.
For best I've owned I'd say it starts at a FWD Audi Coupe, it had bum warmers and winter tires. Blew reverse on it trying to get out of a snowbank.
Next would be my Audi 90q20v sedans, bum warmers, heated mirrors, AWD and winter tires, still, occasionally didn't start at -30 and so-so ground clearance.
Next is my Audi 5000 turbo quattro, bum warmers, heated mirrors, locking diffs, only got stuck once, on a snowplow berm I tried gettting through but ended up high-centered on. Rad froze and exploded one -30 night (guess I should have added a bit more anti-freeze)
Second best is our present Subaru Outback VDC, AWD, bum warmers, heated wiper area on the windshield, heated mirrors, traction/stability control, winter tires, decent ground clearance, always starts... except the engine is now dead and I'm in the process of removing it and cursing it.
Present winter beater, Porsche Cayenne S. AWD (haven't had to switch it to anything more demanding yet, but it has lockable diffs and low-range transfer case) heated seats (best I've experienced), heated steering wheel (in case any Aussies visit), traction/stability control, winter tires. Haven't tried it yet in the nasty stuff but it get out of our snowy uphill cottage driveway with no drama. Will report further once we have some real winter.