Aside from all the shitty east coast mountains, I've skied Breck, Park City, and Keystone. Out of all of them, Keystone A51 was by far my favorite park. Here's why:
-The double chair (can't remember the name of it) only services the park. This means no Jerries/Gapers.
-Keystone also doesn't have as much as a "Family oriented" vibe as Breck does.
-The Alley at Keystone has the best flow out of any park I've ever ridden.
-They have jumps of all sizes and are very creative with their features. The jump line at A51 has some of the most well constructed jumps I've ever hit. Hit every one of them without knuckling or overshooting once.