Yes FF is usually better than crop. As you have seen, the exception is with the 1D series cameras. They are made for professional users and have excellent AF systems and FPS which something like a 5D2 cannot touch. If you are coming from any Rebel series camera, a FF camera is going to make your eyes open wide as you stare at the difference. The one thing that bugged me about my crop cameras is the crappy ISO performance. I think Canon is finally starting to step up, but still lagging begind by a good margin.
yeah i went from a 5D2 to a 1D3 and was glad i made the switch, Now i shoot Sony A6k but i'm happy with the results i have got.