Cantilevers are just about the best braking system out there in my opinion, although I haven't tried disks much. They are a bit more finicky to set up, but they have the added benefit of not only being more powerful, but also more adjustable, and much more versatile.

You can set them up (with no more than an hours work) to stop on a dime, modulate well and never squeal. They can take just about any range of tire you can imagine, and can even have the mechanical advantage modified to suit your taste.

Not only that, but even the cheap ones work well when set up properly. I ran with a set of cheap altus cantilevers, with koolstop pads, and never had an issue, until i switched to some more blingy dia-compes.

Go with cantilevers, read the sheldon brown page, don't spend the hundreds on pauls, it's not that they aren't good, they're just really expensive.