I have both a 6 year old Kapex which has had no issues using as a DIYer quite a bit, and also a 3 year old 10 Bosch Axial Glide that I keep on a gravity rise mobile stand that only gets used on outdoor projects or renos in my house where I'm primarily using for construction lumber. Both are very good saws, but the Kapex is by far the favorite for a multitude of reasons.
It is significantly lighter. I think it's like 44 lbs versus 70 something lbs for the Axial. (Incidentally, I do recall that a 10in versus 12in Axial only has a weight differential of like 2 lbs or so, so it's not like going to a 10in Axial versus a 12in Axial is really gonna save much on the heaviness issue.)
It is easier to dial in miters. The Kapex just shines in this regard imo.
It has far superior dust collection even after having tried to put my Kapex rubber dust chute boot on my Axial which many have done, but still does not bring the Axial anywhere near the Kapex dust collection which imo you never will just because of where the chute is located on the Axial and any other miter saw compared to the placement it is designed on with the Kapex.
Kapex has a better hold down quick clamp when needed. The Festool hold down does not work in the hole for a hold down on the Axial. The stem is too big/fat.
It can do 'stopped' cuts for making slots/dadoes/rabbets whereas I don't believe my Axial has that ability. Something I've only ever needed to do occasionally, so rare that I tend to need to pull out the owners manual to remind me how it works, but the Kapex has that ability.
I've never tried to use the Axial for fine work like in doing trim molding cuts, but that's because the Kapex is so good at this and past experience with other miter saws I just never bothered to try trim working cuts on my Axial.
As somebody previously mentioned, the 12in Axial doesn't do a heck of a lot more than a 10in Axial and with a 10in saw there tends to be more accurate cuts than 12 inch saws for precision type work. That's just a known fact by many. I bought mine on clearance for $232 at Canadian Tire, otherwise I probably wouldn't have bought it to replace a 20 year old Craftsman chop saw which I still use and can't seem to kill, but at that price it was just screaming at me to take one home, so I did. I'm very happy with my Axial, but obviously moreso with my Kapex.
That's all the comparison I can think of right now, but I'm sure there are more tidbits of the Kapex over an Axial. FWIW.