Welp, I sent my faulty FM9 back to Fractal today. I hope I get it or the replacement back next week, but I think it'll more likely be the week after. I don't want to admit how much I already want it back...
I have been playing with the Helix again, and as much as I really don't want to say it (because I love my Helix and the team behind it)... Fractal's amp modeling is on another level. You dig into an amp like the Princeton, and on the Fractal, you hear all these lovely evolving interactions in the distortion that go long after your pick attack. It sounds so organic and realistic. With the Helix, it still sounds pretty good, but it seems like the realism in the models stops evolving much sooner in the sustain and decay. There's also a liveliness in the attack with Fractal that, again, feels really natural and realistic, whereas I have to fight the strings more with the Helix to get the same thing. If I recorded both I think most would have a hard time hearing these differences, but to the person playing it's apparent.