Last year we stayed in Breck--awesome little town. The second day we were there, we drove to Vail, and proceeded to spend the remaining 4 days at Vail.
Breck is fun, but Vail is insane. HUGE. You could spend a season or 5 there and not see everything.
Definitely go with Vail. The size of the mountain, variety of terrain, and overall WOW factor all blow away what Breck has to offer, IMHO.
Lib Tech Skate Banana 159 - Rome 390 - Northwave Legend, Ride BOA Crew
Rome Agent 160 - Rome 390 - Northwave Decade
Ride Society 157 - Ride Beta MVMT - 32 Ultralight
M3 Discord 155.5 - Drake SuperSport - Northwave Decade SL