You truly have not been to Rovaniemi if you think this place is crowded... :) The town center is quite small and most of the stuff you do doesn't happen there anyway. As the nature is so close here, we actually have excellent conditions for any outdoor activity maybe except for downhill skiing.
But still you can't compare the two. Rovaniemi still is a town and Saariselkä a resort in the north. Some like to be closer to a town and some prefer their solitude also in the evening.
For the Santa-part Santa Claus Village (and SantaPark next to it) can't offer the same intimate experience as specialized Santa programmes can. But in winter it is quite a nice place to spend a day. They are building something new every year, and its gradually turning into a mini-resort with outdoor activities, safari companies etc. Not solely relying on Santa which is good.
If you want something more intimate in Rovaniemi, check Joulukka: http://www.joulukka.com/