SPD's, but they do get stuck full of ice. I would consider some platforms or some of those with spd's in the center of platforms as in the bad snow, you are in and out of the pedals so often.
I see a lot of the super fat bike guys running flats so they can run real winter boots and not get frostbite. In places where the Lake's won't cut it it become necessary. Well now those new boots Jim bought are out, maybe those guys can use those.