I use Canti on the rear and mini-V on the front. I found Canti's on the front would struggle to stop the bike coming down a really steep hill, plus they would cause the fork to shudder.
Tektro 720 is good for the rear.
Tektro 926AL work with STI levers (without the travel agent) with much more mechanical advantage so you do have to adjust them with fairly small clearance of the pad to the rim, but they really give tons of stopping power. It also helps to use an adjustable noodle on the mini-V brake so you can use the quick release to open the brake and change the wheel.