In relative terms, a v-brake requires a long cable pull to operate properly, a canti brake requires a much shorter amount of cable pull. Why does this matter? Well, if you do have road handlebars, most road handlebar brake levers only are short pull -certainly STIs only have short pull. Of course, you can use some short pull brake levers for v-brakes by using converters, but (at least from my friend's comments) are difficult to use and install. He ended up not using them. You can also use long pull road brake levers with v-brakes too.

Both types of brakes can cause rack issues, though I'd say usually cantis are less likely to have issues with racks (as well as fenders). V-brakes are much easier to adjust, though this is not as pronounced as it once was as newer cantis use v-brake like brake pads, which makes adjustment far easier. Cantis may also be adjusted by using adjustable cable hangers versus the unadjustable static through cable that come standard on most cantis (a personal note here, I have cantis with a through cable that work terrifically well, but some people swear by the hangers -I've personally not found them necessary).

One thing I do very much like about cantis is that I find them to have a greater degree of modulation, whereas v-brakes tend to be very digital -either on or off. This can be certainly exacerbated by poor brake pads (Shimano supply concrete brake pads, I swear!). On either brake, I'd recommend Koolstop salmons -a brake upgrade that is a huge bang for the buck as far as I'm concerned. On the flip side, V-brakes are much less susceptible to off true rims as they sit further away from the rim, and are incredibly easy to adjust. If I was pushed to give a preference for either brake, I'd have to say cantis. However, both brake types, assuming they are well setup and of reasonable quality, are more than fine IMHO.

Course, my touring bike has Avid BB7 road discs anyway..... which I do consider to be the best choice for the type of touring I do, and certainly out perform most if not all v-brakes/cantis in wet braking as well as power (just my opinion!).

On a final note, cantis are nothing to do with fashion, being retro grouch or accepting inferior or dangerous braking for heavy people (that's me!) -that's just plain ridiculous and inaccurate. Well set up good quality cantis are fine, as are v-brakes.