I have a rigid Miele MTB that I ride al through the winter. I had it with cantilever brakes properly set up but wanted better braking in the snow and slush. I converted it to V-brakes and even without the better stopping ability of KoolStop pads the bike stops when I want it to. The limiting factor for me now is the grip the tires have on the road. I find it quite easy to skid a tire in the snow or slush so disc brakes would NOT be an IMPROVEMENT for ME. YMMV
Oh, that bike has a dropbar handlebar and Tecktro V-brake brake levers.
Cheers