Only being here in CO for two seasons, I have somewhat limited knowledge, but here's my two cents. I like BC over Vail by leaps and bounds. One, the crowds at BC are non-existent. I was there on the busiest days of the year and the best pow days of the year, and never did I wait more than a minute. Second, on most of the runs, there's a challenging run near a nice easy blue that meet at the bottom- so you can go one way, your beginner/intermediate can go the other, and you can meet at the bottom. Also, the service at BC is beyond expectations... an escalator to transport you, a chef giving away freshly baked cookies, great staff, nice patrollers and lifties... man am I glad I have a season pass there and get to enjoy the poshness created by the others who are paying out the arse for the service I get for next to nothing.
In terms of lodging, personally I would try to get a place in Frisco or Breck and make the drive to BC and/or Vail. The price is so much cheaper, and all its really costing you is a 30 min drive in the morning. Frisco and Breck are both great towns with plenty to do. Granted, they're not as ritzy as BC or Vail, but they're not lacking in character and class either. That way you can even mix up where you want to ski- Breck, Keystone, BC, Vail, etc... you realy can't go wrong anywhere.