Well, I've skied Crested Butte (once) and Heavenly several times (though not recently). So take this with a grain of salt, and a prod to get the more frequent visitors to chime in.
Crested Butte:
It takes a lot of snow to cover the good terrain, and January is a bit early for that.
A lot of the good terrain requires a moderate hike to get into (a traverse with some climbing) or to get out of (psychologically much harder, at least for me). There is still plenty that doesn't require any hiking, though.
I think the view of the town from up on the peak is better than most "pure nature" views, though your taste may differ.
A really cool town. Good free seven minute shuttle from the town up to the hill. There is also an option to stay in the village at the base if you want, or in Gunnison if you want cheap (half hour? hour? I forget.) There is, or at least was, public transportation from Gunnison to CB available.
Heavenly:
As Phil said, a few pods of very good terrain mixed in a lot that isn't. It takes a long time to get around the hill, and is nearly impossible if the upper lifts are on wind hold. If you have to return home on the California Trail at the end of the day, there are a lot of unguided missiles to watch out for.
There is enough elevation difference between the town and the hill that you often have lots of snow on the mountain and very little in town, making walking around in the evening more pleasant.
I may sound a bit negative, but I wouldn't turn up my nose at the chance to ski either of them.