I've used the Campy, the base Shimano, the Dura Ace, Sunlight knockoffs, and Origin 8 black boxes. Once they're installed, you pretty much forget them, unless you have a cable stretch or some issue. I've had them "save" shifting a couple of times, mainly because I was too lazy to stop and adjust at the RD, but I've used the L one to get some extra pull when I headed out on a bike that shifted fine on the rack, but the FD wouldn't stay on the big ring under way.

Simply put, buy for appearance and call it a day. They all work. I'm not sure there are any high end ones, market is probably too small, but you knever now.