Ive owned a Kemper since January. Ive had a couple of axefx2 over that period but ended up selling them both (not both at the same time lol).
Like you I prefer the Kemper for amp sounds.
FX wise I didnt find any difference in the quality but the axe2 certainly has a lot more routing and tweaking options, (much more than I needed) and a lot more fx available.
Ultimately I found the axe didnt give me anything extra that was of any use to me other than the pitch fx, which I hope will eventually be available on the KPA. In the meantime I preferred the eventide pitchfactor to the axe for those fx so the axe had to go.
In the end, IMHO the KPA has better amp sounds/feel (up to firmware 6 on the axefx) and the additional fx capabilities with the exception of pitch fx were of little use to me, but can see how they would appeal to a power fx user.
Not a big fx user anyway, but I would like to see how the Kemper sounds in the loop of the Axe.I like the "ala U2" stuff in the Axe II (shimmer, multidelay....).And the reverb in the Axe is awesome.You can make some delay / reverbs routings for certain sounds that by now you can't do with the Kemper.Maybe I'll keep both units maybe not, have to make more tests comparing certain things I want to check in both units, but I addmitt that there's an "instant pleasure" sensation when playing with the Kemper, and tweaking is minimum.