Several years ago I built a winter bike with a rear disc brake and front V-brake. My commute did not have enough stops to keep my rims clear of ice when riding through slush. If the rims ice, no brake pad will work. Disc brakes are 13 inchs above the road, which still gets them 8-9 inches away from the yuck. They make it possible to have predictable braking in the snow-freezing rain mix we get so often in New England. If you don't have those sorts of conditions more than 3 times a winter and have other non-bike commute options for those days, rim brakes will be fine.