I don't want to reopen the debate of which is better but just want to offer my user experience.
I have used a full Shimano Ultegra Triple group for the last year and just built a new frame with a mix of Campagnolo Record (crankset, chain)/Chorus (derailleurs, cassette)/Centaur group (shifters) also in triple.
Here is my first user report:
1) The Campagnolo front derailleur is a lot easier to setup and adjust.
2) I am still getting used to the Campi Ergo system but both are good and smooth. So this is pure question of taste.
3) One major advantage to the Campi system is front shifting on a triple system. Shimano offers 4 clicks, 1 for the large chainring, 2 for the middle (1 when using small cogs, 1 when using large cogs), and 1 for the small. My experience has been that shifting from large to middle ring is fine but shifting from the first middle ring click to the second is very sensitive and often results in a direct shift to the small ring. Campagnolo offers a total of 8 clicks allowing for minute adjustments on each ring depending of what cog is used and thus avoiding noisy combos when the chain just brushes the side of the derailleur. I also noticed that the clicks are more positive avoiding accidental jumps to the small ring; I have had none of those so far.
4) The Shimano shifters might be more convenient when downshifting while braking. Again I am still learning the Campi stuff.
5) My Shimano cassette was 12-27 (9 speed), the new Campi is 13-26 (10 speed). I am missing the 12 cog but appreciate the intermediate cogs that makes shifting smoother. I wish Campi had a 12-26.