I was present at Crank 2 while a couple tested several bikes with different braking systems. Their feedback was pretty revealing:

• V-brakes are the weakest of the 3 they tried.
• Disc brakes tend to be noisy and wobbly while doing high speed braking (may be an installation issue as we haven't seen wobbly rotors yet on our Co-Motion).
• Dual-pivots were the best of the three due to stopping power and smoothness during high speed braking. They were also very silent as compared to discs.

Don't rule out dual-pivot systems yet, marco. If they fit, they might work for you, and shave a few grams to boot!