I have both and they are both top notch, the Axe fx has the advantage of a really nice editor, dedicated midi controller and tons of effects and routing options. The Kemper is easy to setup and get some really nice guitar tones. Disappointed there has been no editor/librarian released or the dedicated midi controller. If you can get both, do it and consider yourself fortunate to have the best of both worlds.
Yes, I agree
For my cleaner, plainer amp sounds, I have only ever found/tweaked a few clean patches I really liked on the AF2, and nothing that every felt/sounded much like my favourites: my Dc30 or Ceriatone BM (John Mayer Type Dumble clone)
Straight away, on day one, from the free shared KPA patch database, I have patches that are close enough to these 2 for me to enjoy. Certainly at present, the simpler cleaner patches with a lot of amp feel that I often use are more plentiful on this KPA
I have not been too impressed with the metal/rock sounds on the KPA so far, and the FX are a bit fiddly from the control panel (although that is compared to the main controls - still easier than the AF2 I suppose). Having the dedicated Bass/mid/treble/presence is such a pleasant change, along with the input gain and volume controls
I suspect the amp sounds I want are in the AF2, but most owners seem focussed on heavier sounds, and I haven't yet pulled the sounds I need from it, whereas as I said - the sounds I was missing were available on day 1 with the KPA
Other observations: KPA is not as heavy or solid as the AF2. Who cares though, it lives in a rack
KPA has no fan - what a relief
KPA does not try to blow your speakers when you power off if you forget to mute it first
AF2 FX are way better, editor better, routing etc
KPA deals with different guitars & pickups better (clean sense, input gain knob etc)
My conclusion: choosing between the AF2 and KPA is like saying "you can only have one of a strat or a Les Paul or a 335" - they are all pro instruments (and I do believe that top amps, AF2 and KPA are instruments) that cover different needs, and I will be keeping both. I have too many valve amps already, and selling one that I rarely used bought me the KPA and 2 new guitars