I bought a second handed FM3 a month ago because I was curious about the possibilities. I also mainly use the same Kemper profiles (Michael Britts and Bert Meulendijks profiles). I must say that the FM3 is a great unit with a lot of great sounds and a lot of possibilities, but when I compare the best Kemper sounds I can get to the best FM3 sounds I can get, the Kemper wins. Maybe the comparison is not very fair because I own Kemper since 2013 and I own the FM3 for only a month, but the amp sounds in the Kemper just sound a bit more raw, more amp like to my ears. Especially in a band situation, the Kemper definitely wins.
Of course your opinion can be different and there is only one way to find out and that is to try out the FM9 for yourself
i look forward to comparing, although I know it will take some time Get the fractal dialed in. Kemper took me 1-2 years to enjoy but I think the education I gained in tweaking digital parameters will speed up the fractal learning curve.