I don't like cantis very much, v-brakes are generally more powerful. Good modern cantis on a 700c wheel are pretty good, but cantis on a 26" wheel are weaker.
V-brakes on a 700c wheel are often more powerful than smaller discs on the same wheel, but good disc brakes on a 26" wheel are usually more powerful than even good v-brakes (on the same wheel, due to the radius of the rim braking surface vs. radius of disc braking surface) .


I cant's stand old school cantis with the posts. I have a set on my city bike in the rear, and they're a little annoying to adjust, and give little power. These are the really old school ones on an early 80's mtb, which have the holes for the spring on the outside rather than on the inside. I might resort to welding on modern v-brake bosses.

Also, v-brakes with cantilever levers do work, but you need to have a barrel adjuster and keep your pads close to your rim, and a good wheel that won't go out of true. Then you have tons of power, but modulation is tricky.

Cantilever brakes with v-brake levers give tons of easy modulation, but pathetic power.

That's my experience.