Re: 13.04 should be dedicated to performance.
You'll not see the same issue with Kubuntu and KDE as you perhaps might with Unity. I have run both very recently and they are both fast enough on my system. However KDE has some great options, one in particular tickbox allows you to suspend effects for fullscreen windows, a feature that Unity does not have. The result of this is that video and games tear and slow down when running fullscreen on Unity, where KDE, and even Gnome Shell and Cinnamon do not.
Originally Posted by SeijiSensei
I'm sure I read on Launchpad somewhere though that the developers were aware of the problems and were fixing them.
AMD Phenom X4 945, 4Gb Crucial 800Mhz DDR2 RAM, 1Tb SATA III HDD, AMD Radeon R7 250X [Oibaf]