Penates, welcome to THR. Step one(if you already haven't)is handle them both and see which one feels best to you. If you don't reload, 9mm costs about half as much as .45acp, if ammo cost is important to you. I have no personal experience with either of these two particular pistols, so please keep this in mind. I have HEARD that FMs are usually ready to go out of the box and that the RIA 1911's sometimes need a little tweaking. Hopefully some owners will chime in shortly.
-jagd