Do any of you that have both get on your FM3 and say "man I really miss X on my FX3"?
Both units here. AFX3 for studio, FM3 for live/rehearsal. I only miss just a bit of CPU power, but that almost made me return the FM3 and keep an FXII for live use.
I only used dual amps for seamless changes in-song and thought that was going to be a showstopper for the FM3, but, truth is, scene changes with different channels are so fast that I can live with them. YMMV here though.
I did not thought I use extremelly complex presets (I do not use textured delay/synth soundscapes live, for instance), just a fairly basic sound with a bit of delay, reverb and chorus for soloing and a couple of compression tricks to tighten things up. Then add a pitchshifter for dual guitar simulation...
...And I was not able to squeeze all of this in the FM3. I had to make a couple of compromises. That means definitelly ditching the CPU hungry reverb block and substituting with other blocks (e.g. Plex Delay, following the excellent Leon Todd's tutorials), which I find OK for live use.
Would I be able to live only with an FM3? Yes.
Would I have to make some compromises and tricks, and still only be able to reach 95% of where I want in a preset? That's a yes too.
Edit to state the obvious: I finally settled with the FM3 and sold the FXII because of portability. I think it is an absolutelly fantastic product at an awesome price point.