You cannot compare KPA vs. tube-amp, that doesn't make any sense:
The KPA is mainly built for playing it straight into the desk, if you have a good monitor situation, the KPA will sound awesome, if your monitor-situation is bad, the KPA will sound bad.
Much easier with a tube-amp, plug in your guitar and there's the sound, but whereas the KPA already has a perfect signal for the mixing-desk and P.A., you have to mike the amp up and try to get a good signal for the P.A..
In my normal stage-situation (big venues, in ear) the KPA normally will sound much better than any tube-amp, miked up and standing somewhere...And the FOH-guy will love it, because there's no loud guitar-signal on stage crawling into all mikes.
If you play in a club or on smaller stages (probably like fretboardminer) and maybe the amp is not even miked up, you will get a good guitar-sound with a simple tube-amp very fast. If you want to have the same quality with the KPA you need very good FRFR-cabs.