Tough call, esp since you already own the FA-07 which makes it that much more cost-effective. But the obvious things you'd lose would be the drawbar organ engine, the sub out, the trigger pads, the sequencer. Most of the Yamaha sounds should be better at least than their non-SuperNatural Roland equivalents (the other SuperNatural acoustic tones in the FA are piano, EPs, clav, basses, acoustic guitar, ensemble strings, which are areas where Roland could have an edge). In synth sounds, Roland should lead in virtual analog, Yamaha in FM. Seamless sound switching is more extensively implemented in the Yamaha than the Roland (for a change). Action will be subjective, but I expect that the Yamaha will at least be more even front-to-back, which should make it better for pianos. Ability to load custom samples ia a nice Yamaha perk, too.
You can pretty much always find one person who will say anything. Especially at gearslutz. ;-) Seriously, again, actions are subjective, but I bet that will very much be a minority opinion.
I've owned the FA07 and Montage.... The yamaha sounds cleaner, especially for FM type sounds. I'd say Yamaha has it over Roland for the EP's, organ sound well i never really used either too much as used KB3 on my kurzweil instead but say they are pretty close.
Where I preferred roland was for synth sounds, especially pads.... the Roland Jupiter type sounds are really fat sounding, when layered they are killer. I always struggled to get the same fatness out of those kind of sounds on the Yamaha. Its really depends on what sounds you use most.