I was a mostly-happy Gnome (that is, vanilla Ubuntu 18.04) user for almost a year. I liked almost everything about it, really. The big problem is the fact that extensions are written in JavaScript and have no sandboxing of any sort, so that when Gnome updates and some incompatibility with an enabled extension is introduced, Gnome crashes on login.
I disabled all my extensions from the Ubuntu recovery console. While this made it so I could log in, it didn't stop all the crashes. Clearly there was still just some instability with Gnome.
So I switched to KDE. KDE required a lot more configuration to get it to look and feel right. Probably a lot of that was due to residual configuration from the Gnome installation. I imagine it's much smoother getting started with Kubuntu directly. But I was dismayed to realize that KDE too was crash-prone. After a few months, it eventually got to the point where it was crashing every time I closed my laptop lid. At that point I switched back to Gnome, sans extensions.
Both Gnome and KDE are pleasant to use, except when they crash. They are bad when they crash.
Gnome has more reasonable defaults; it makes more sense out of the box. KDE has more cool features – a vertically-split file browser is what I want basically 100% of the time, and I didn't know it until I used KDE.
But the way Gnome does extensions is irresponsible to the point of insanity. There's just no hope of having a stable system like that. A huge ecosystem of extensions has sprung up based on a software design decision so abysmally bad it could only have been an afterthought.
I imagine that the crashes on lid-close-lid-open have to do with shitty drivers for my hardware, so as a warning to future generations: I'm using an HP Spectre x360.