I asked the most experienced mechanic at the bike shop what makes dual pivot sidepull brakes work so well. His quick snide comeback was, "They have double the pivots!"
It looks, by the design, that it has more leverage, but then the lever might have half the leverage. The amount of travel at the lever is about the same. So what makes them stop better?
A more general question: what good is improving the leverage of a brake caliper? V-brakes clearly have a lot more leverage, because the end of the arm, where we attach the cable, is very far from the fulcrum. But to counteract this, we use levers that have LESS leverage. Are we back to where we started? Or is this inherently better in practical use?