Yah you don't REALLY have to decide as far as skiing because they're so close and there are free shuttles. If the actual New Years scene is what you're looking for though, probably Breck. Make another post in late December to try and score an invite to a house party though, the bars will be crowded with assholes/vacationers and it'll be hard to get into a local party randomly unless someone is chill and knows you're coming, people in Breck are very wary of tourists. I'm moving out that way in late December, so I'll either be in one of those towns or Denver for New Years, if you repost in a month I'll let you know what I'm getting into with my little crew. Good luck mang! It's going to be fun out there this year.