What I've noticed is that most (not all) of the AxeFX (and not the AX8) endorsers use it for its FX, not for its amp tone. This is easily verifiable.
The Kemper, on the other hand, is used for its amp tone by its endorsers. And it's FX are not as diverse as the Axe, but they are definitely high quality. And some are unique, like the pitch shifter with pure tuning, or the morph effect. What's more, there are more FX being developed by the good folks at Kemper Amps.
I know which one I would want from a do-it-all box.