Ubuntu vs. Kubuntu - Game Performance

[Shibblet]

Was excited to do a fresh install of Ubuntu 18.10, and got it all loaded up with my favorite software. Along with Steam and Proton, I could start playing some of my favorite games. I noticed that the game didn't perform as well as it does in Windows (The Witcher 1). Well, I chalked this up to being played on Linux, which is a common thing with windows games.

But then I decided to load up Kubuntu, to give it a test whirl... and the performance difference was very noticeable. Even just the DE seems snappier and faster.

Well, the game performance was significantly better in Kubuntu as well. I couldn't tell any performance differences between Kubuntu and Windows.

Any ideas why Ubuntu would be slower than Kubuntu? Isn't KDE more resource intensive than Gnome3?