Quality and capability on the two are for all practical purposes, the same. I built my dream road bike last fall with Chorus, because:
1. you can take the components apart and replace individual pieces.
2. My old college days road bike was all Campy Super Record. Lasted forever, a joy to maintain.
3. Just personal taste - I thought the Campy components were so beautifully finished.
In all fairness, the lifespan of DA equipment is so long that it's unlikely that they'd need repair anytime in the next few years.
It's a little harder to find wheels that will take Campy 10 speed cassettes, though Campy itself turns out an excellent line of wheels, and you can buy (a bit expensive) Shimano cassettes that have been converted to Campy 10. I don't know if the upcoming DA 10 speed would work with a Campy chain/indexer.
The brake handles/shifters feel different. Try them both, I preferred the Chorus levers, but you may not.
There will be a DA 10 speed this fall. It means that either you can have a DA 10 speed, or a real bargain on a DA 9 speed.
If you go with Chorus, take a look at cbike.com - they had the best prices on a Chorus group last fall.