Also, curved automation is not important. If really required, you can just spend the 5-10 seconds and add more breakpoints. At any rate, Ableton 9 will have curved automation

The lifetime free updates are pretty cool, though. Consumer-wise, FL dominates Ableton's prices.
Apples and oranges. Sytrus is the only FM synth out of the ones you mentioned.
I do think it boils down to if you really want Sytrus and Maximus or not (and also Harmless is a great synth too!).
Oh, I agree. I just meant that if I was going to synthesize a sound in general, I'd almost always prefer Sylenth or Massive. If I really wanted to use FM I would use FM8. I'm not denying that Sytrus is a great little synth, I just think there's better options out there.[/quote]
Aesthetically, I really like Ableton's minimimalist design the most honestly. Although the new FL betas are looking good as well. I just don't feel at ease with the way Ableton is layed out though. But I'm really hoping that FL would take some ideas on how Ableton handles track freezing and recording as they look more intuitive. Fortunately Gol (FL's main developer) seem to be less of an A-hole nowadays and is really listening to what users have to say. And yes the detached windows can get a bit messy but I think their working having an option that can make it lock in place. What I often do is use the sequencer, piano roll and the mixer on one screen and maximize the playlist on the other screen. Also I'm not that big of a fan of using automation clips, I prefer using the envelope controller for my automations.
I would rather have Abletons Operator over Sytrus as it looks more user-friendly. Toxic Biohazard is an easier FM synth to learn. Don't just get FL just because Sytrus. Gol himself said he has no future plans for Sytrus and it could be phased out since it was developed on an obsolete programming code or something. UI on Sytrus is not that good and Gol has no plans of changing that.