Personal preference I think...

people have already pointed out:

1. Shimano isn't really set up to be repaired. It's meant to be replaced when worn out. Campy on the other hand are meant to be repaired.

2. Shimano shifts smoothly so you don't get that positive action you can feel as you would with campy.

If you are not racing I think you can't go wrong with Centaur, Chrous for campy and 105, and Ultegra for Shimano. You pay lot more money for Record, and Dura Ace, you really wont notice the difference from the Centaur/Chrous/105/Ultegra. And that extra 1/2 lb saving isn't worth the cost.

Sram is pretty nice but I too have heard of premature breakdown.

Personally, I'm not fond of Centaur. tad slow in shifting and I prefer a quiet yet positive shift. For a recreational and serious weekend rider, I think its still a really nice group. I like Dura Ace, Record, chrous, and ultegra. 105 is tad slow in shifting for me.

Ultegra rear deraillure will hold up for about 5,000 - 10,000 miles. STI brakeset/shifter also about the same distance. Then its time for a new one. Over the years, I have managed to mangle two ultegra rear deraillure, one ultegra front, one shimano-600 (precursor to ultegra), STI brakeset... Most had a minimum of 5,000 miles. They all went well beyond "time to replace".

Centaur is on my "new" used bike and haven't logged that kind of miles yet so can't say. Record and Dura Ace will hold up a little longer than Ultegra. Again haven't had the luxury to ride them into the ground. Its just my observation from others.

Braking issues. really none that I can think of. They all do the job well. Dura ace has a strong braking action ultegra little less. Centaur brake set is real positive. Maybe tad too sensitive on the rear wheel. It has a tendency to grab and lock up the rear. (maybe its my setup don't know). Chrous and record also work really well. All these brakes work well even when the wheels get wet.

The whole thing comes down to personal choice and how well you can reach the control from the hood or from the drop.

The best advice from me is to see how easily you can reach the control and then decide.