However, it would be wise to check the Vail web site and see what conferences or events are schedule at the time you are considering. At times in the summer Vail can be overrun with youth sports tournaments.

I've never been able to find anything nice to say about Vail (sorry to all the Vail lovers of the world).
I'd prefer Breckenridge over Vail, but there's something a trifle artificial about Breckenridge.
I love Aspen, however, just to show that I'm not a total negative person.

I think you won't go wrong with any of the choices! I don't get to go to Colorado this year except a brief Denver trip, so I am envious!