Don't know about Breck - never even skied there.
But I know about Vail. If you're there during the week, you'll be fine unless it's Presidents day. Fine meaning no crowds, ski where ever you like.
If your crowd is blue/black skiers, I'd have straight back for the bowls and Blue Sky Basin and stay there. If you're at Vail on the weekend, the crowds still might not affect you, but there's more of a trick to staying away from them.
First, be on the lift at 8:30. Most of the tourists don't come out until 10ish. Then, head back to the bowls. Ski there until about 10:30, then go to Blue Sky. Ski Blue Sky until about 1 or so, then go back to the bowls. This is what I do. What you're doing is staying ahead of the crowds, then back tracking once they've caught up to you. Note. If the poma is running, do laps in Mongolia. Nobody ever goes back there and the skiing is fab. To get there, take Orient Express, then get off to your right. Follow the catwalk around and it takes you to the poma that serves Mongolia.
The other idea is ski Beaver Creek on the weekend. If you ski the upper lifts, even on weekends, there's never a crowd.