I would choose January, for 2 reasons mainly...it's sooner than the other two dates...and we've never gone in January. I'd like to try the parks when they're not so crowded. We did February a few years ago and it wasn't too bad. A few cold days, but better than at home. Our last 2 trips were in April and it is beautiful, however, it is crowded and if you have any little ones, the heat can get to them sometimes. But on that note, we've just decided to go again...in April. Only because we don't want to pull DS10 out of school this year.
anytime is a good time to go to Disney! And the weather is always better than in Michigan!