As far as I am aware, they are very different programs.
Ultra is a real-time chromakey program, specialised to do exactly that. It also has a faintly bizarre feature that enables you to use pre-designed 3D sets.
Chromanator, on the other hand, is a general compositing application, which gives you a huge variety of options. It's also considerably cheaper. You can check out some of the possibilities by browsing the tutorials:http://fxhome.com/support/tutorials/list.php?cat=1