I boarded Vail, Copper, Breck and A-Basin last year and thought A-Basin was great! We spent most of the day in the back bowl which is kickass. We were 5 guys and 3 of the 5 were intermediate boarders and a skier and all handled it prety well. It's pretty rustic. Uncrowded, no-frills, unpretentious, not extreme. I think you'll like it, though, as a boarder, of those you mentioned, Copper was the best! Lots of wide-open, nicely-pitched runs. Vail was a bit better than Copper though.... maybe because we got a powder day there, or maybe beacause there's just so much terrain!