Where are you staying? If you're staying in Summit County (Frisco, Dillon, Silverthorne areas), I'd go to Copper of your choices. Winter Park is about 1.5 hours from Denver and 1.5 hours from Frisco, on good days. Awesome place, love WP especially with Mary Jane, but it is kinda out there all alone.
Personally, my favorite places in CO:
Loveland--over 50% above tree line, not crowded, more a locals area. Great terrain and powder
Steamboat--awesome powder, more isolated so a little less crowded
Vail--the back bowls are 2nd to none in Colorado
Copper--great variety, bowls are decent. Love the setup w/ about 1/3 of the mountain devoted to greens, blues, blacks each with not much overlap so if you're in the blacks you won't have to worry so much about a trail merging with a green full of people learning and going slow. On the same idea, if learning, great to be able to stay over in the mostly green area with people of generally similar abilities.