use Helium Frog. I think it might be compatible with some still cameras. What's your camera?
As for which one of the two I would use if I could only use one of them, I'd go for Monkey Jam. I think it's a good program, but what really makes it suck is that there's no onionskinning. You'd be better off using a film camera and doing it the old surface guage and pointers way. Movie Maker works, but I'd go for AnimatorDV if you want to do what movie maker does. It's free, it does have onionskinning, and it allows you to import your frames, and choose the frame rate.
Youtube Twitter AIMSkype: Kytyjaw11