I own an XP-80 and have messed around on the Triton and the Motif before. In my opinion, the XP-80 is far and away the best of the three - I seriously considered the Triton and Motif before buying the XP-80, and this was only a few months ago (when the XP-80 was already out of production!). It's got a wonderful interface, including a graphical display conspicuously lacking in eye candy and rather good at being functional. Most keyboards these days try too hard to have a computer screen, which, for a keyboard, is just a pain in the butt. The XP-80 also has a great (not perfect, but great) sequencer, a great selection of expansion cards available, and (drum roll here) it looks way better than the other two. The Triton and Motif have annoying control panels (bad design, bad layout, vexing buttons), which was one of the major things that turned me off of them. I'll admit, however, that all three have, more or less, good sounds.

I would get the XP-80 any day - even over the Fantom.