grolby

Um, where do you get the idea that canti brakes aren't as powerful as calipers? When cantilever brakes first began to come into common use, they were rather considerably more powerful than many calipers. The gap has basically been closed, with modern dual-pivot caliper brakes and cantilevers being roughly equal in terms of braking power, these days, but cantilevers have an established reputation for better braking than calipers, and for good reason, despite the decreasing relevance of this reputation. The gap in braking power between discs and rim brakes is really not particularly relevant, however, as ALL modern rim brakes, when properly set up, are perfectly capable of locking either wheel. The arguments for disc brakes that make the most sense to me are that the modulation is better (something that I've never had proved to my satisfaction, but it could be so, and I haven't used discs), and that they are less likely to be affected by mud and poor weather than rim brakes. Since discs are not race legal, these are presumably the primary reasons, along with tradition, that cantis remain the most popular kind of brakes on cross bikes.

EDIT: Low-profile cantis do not have superior power compared to wide-profile cantis, which in fact exhibit superior performance in almost every way. The wide arms grant them better mechanical advantage, and the mechanical advantage does not change as much as it does on low-profile cantis as they move closer to the rim. The wides are generally easier to set up, as well. Low-profile cantilever brakes came into being primarily because of heel-strike issues on smaller MTB frames, not through any particular virtue of performance. The design of wide-profile brakes is simply better, and it's a shame that they are so hard to find these days.