A few things to consider. The choice of brake depends, largely, on your shifter/brake lever setup. If you are going to use STI (or think you want to in the future), using cantilevers is easier in terms of compatibility and set up. If you have separate levers and shifters or if you have flat bars (or want to go with them), linear brakes are easier to set up.

Fenders adds another level of complexity. I've tried to use fenders and V-brakes in the past without much success. Because the arms squeeze in while braking, only the narrowest of fenders work with them. Cantilevers are much more forgiving when it comes to using fenders.

I have bikes with both and they have their advantages. The linear brake is dead simple to set up. Cantilevers are a bit more futzy but they offer a more clearance and they play nice with STI. If you don't run fenders on the bike, choose the Avids. If you need fenders...I do sometimes use them... and want to use STI shifters, run cantilevers.