No lines, uncrowded slopes, lots of runs
Slightly tougher terrian, easier runs accessed by slow lift
A group of four families visited Big Sky to ski 1/1/2013 - 1/4/2013. Having been to Breckenridge over Christmas a few years ago, we knew we wanted a place with fewer people and less waiting. Big Sky did not disappoint. We never waited in line more than a minute or two and often could ski back to the lift and get right back on. That part was great. It also meant that the slopes themselves weren't all that crowded, which was nice for our group of beginners.
The only real downside was that, for our group of beginners, some of the greens seemed more like blues at other places. Especially off the Southern Comfort lift. This meant we pretty much were limited to the Explorer lift, which has several green runs off it that were better suited for our group. However, it's a 2-person lift and is a little slow.
Overall, it was a great trip. And understand that my only negative is for very timid skiers (most of our group this was just their 2nd time to ski and they do not like to ski fast). If you're comfortable on blues in most places, you'll enjoy the greens and maybe the blues at Big Sky.