What sold me on Campy was the thumb shifter and the smaller gearshift near the brakes. It requires less "throw" than the Shimano shifter, which is the same as the break lever if I remember correctly. For what it's worth, you can shift and break at the same time since the levers are different.

And, ditto on everything said above. The systems do sound different, and people have described Shimano as smoother. I wish Campy came with something like flight plan, which seems like a really cool gizmo.