Replying to Keystone or Copper Mountain ?

Hi, I'm going to Colorado for a ski trip but I'm not sure which mountain is better.

I've been a few times in Keystone, Breckenridge and Vail but this time we're thinking if we should go somewhere else.

Aspen is to far away so I was thinking on Copper Mountain.

How is Copper mountain if compared with Keystone ?

Thanks.