First glance... judging by appearance, Kubuntu can be said the "Cool" derived version of Ubuntu linux system. With the KDE Plasma Desktop, the look of Kubuntu is much more fresher and eye-catching. However, in terms of STABILITY, Ubuntu is much more stable.
I've tested install and run Kubuntu as a vm on my VMWare Player. The installation process takes much longer time (compared to installing Ubuntu), I've no choice but left it running overnight. After the initial installation, I started download patches and upgrades, crashed... and crashes. Programs like media player also experienced frequent crashes.
The overall performance is slow when compared with Ubuntu, displays dragged and initial screen draws were messy... New windows pops up with distorted screen, then redrawed.
After a reboot, the mouse is lost!! Reinstall VMWare Tools failed... really disappointed...!!
Eventually, I removed the whole Kubuntu virtual machine ... go back to my Ubuntu virtual machine.
The "cool" look of Kubuntu, ... yet sadly buggy ...