My two cents: At the mid and high levels of each range, they all work extremely well provided they are properly adjusted. The biggest thing may be which brand's levers feel most comfortable to you. I have a Campy bike (Centaur/Chorus 10-speed mix); 2 Shimano bikes (DA/Ult/105 9-speed mix); and a SRAM bike (Red 10-speed).

Campy: I love the micro-adjustable FD, which means that chain rub is never an issue. I hate that the cassettes are ridiculously expensive, and I've never gotten used to the thumbshifter.

Shimano: robust, always works, but the levers have never felt comfortable in my hands

SRAM: my new favorite: easy to set up, shifts precisely, but the double-tap takes some getting used to.