I have run disc brakes on my mtb and loved them for the power and modulation they offered but also do not feel like I am at a loss when I run rim brakes and any decent rim brake, be it cantis, centre / side pulls, or v brakes can provide more than adequate stopping power if they are properly set up.

The bikes I ride that see the crappiest conditions all have cantis and stop just fine in the rain, slush, and in the snow and I have never had an issue with them not stopping me when I needed them too.