In reply to dingbat46:
Driving on a fairly level but windy A road on 20cm wet snow/slush doesn't require 4wd, low box and difflock. Of course as this is UKC and I drive a BMW it is a given that I wasn't driving to conditions. Sarcasm aside, yes I was going too fast, not so much for the actual road conditions but for having anything in reserve if I had to make a sudden maneuvre to avoid an oncoming vehicle, which I did...
Difflocks, 4wd and the like will give you oodles more traction, it is true. But traction is secondary to being able to turn and stop, which is why I'd rather have any car with winter tyres than something heavy with a high centre of gravity.
Forestry tracks, moorlands, quarries, the Sahara Desert and towing huge trailers aside of course.