Adam Garstone at Definition Magazine gives a quick overview of these 3 powerful 3D Compositing Programs. Work a read.
After learning Shake years back I would love to get into one of these, but can’t afford either Nuke or Smoke, but once a free Mac version is released of Fusion by BlackMagic Designs I will probably spend the time to learn it, and hopefully they will have added a good 3D camera tracker by then.