105 derailleurs work just fine with FSA compact cranksets. FSA says theirs are designed to work better (and the shimano ones may have to be fine tuned in setup, a little more carefully than on a standard crankset). I only have experience with Shimano and not FSA FDs, so I can't really compare. I do know that you can make a 105 FD or Ultegra FD work just fine. Is the FSA easier to tune? I dunno.