Better, in many cases actually. The gravel mixes with the snow, and for added traction you just run a sander in your road plows (with actual sand, not that calcium chloride/salt mix they mostly use on pavement now). Fun fact about putting salt on the roads to melt snow and ice: when it gets cold enough, it starts refreezing and gets slippery than a bastard.
If given a choice, I think I prefer driving on poorly plowed gravel roads over well plowed paved roads in snow storms. Gravel roads don't seem to ice up as easily, and the gravel and dirt helps with traction.