Same firmware?
Maybe his valves are more worn in 
lol
I've got 2 KPA's (toaster and rack) and mine sound exactly the same
Output EQ?
Clean sens?
Vintage Kemper rules 
My Kemper is vintage one , as first, and as second , yes, I did replaced originally tubes with boutique ones . 
Maybe noise gate.
No, aging of numerical program.
It is proved.
Fashion of vintage software
Some of bugs make age the program after a long time.
It's the begining of butterfly effect .
Different poweramp? Different something?
I honestly would find it really strange otherwise...
Different firmware,
but everything else is the same....clean sense...etc.
I was VERY thorough.
Which firmwares exactly???
Only way to be 100% sure of having global settings the same is to do a system reset.
Twice I've noticed my profiles not sounding the same and this cured it. Both times after using the early beta rig manager. So maybe in switching all those profiles, something got stuck.
But it hasn't happened lately.
Have you isolated all the other stuff, that is, all the peripherals are the same? (I'm sure you did this, just throwing it out there)
OK, I made joke, thinking everything is the same , including firmware.
Now , this is proving my theory that different firmwares sounds different , especially last one, 2.4.2 .
Never considered that the firmware might caused the difference, it was easier to assume it was caused by hardware.
Anyone want to test?
OK, I made joke, thinking everything is the same , including firmware.
Now , this is proving my theory that different firmwares sounds different , especially last one, 2.4.2 .
