I'm pretty biased since I have been using KDE for a few years and only switched to Gnome this week to properly try it out so maybe I'll change my mind but I doubt I will.
IMO KDE has better theming and is more uniform across a wider variety of apps. It has support for community themes out of the box and it feels like the components are modular so you can have a different colour title bar compared to the app window etc
- Dolphin > Nautilus
- Kate > Gedit
- Konsole > Terminal
These are the 3 main default apps I use on both DEs. Dolphin has way more customisability and looks better but Nautilus has a fantastic multi-file rename with the option for find and replace built in.
For me, Kate is like the vlc of documents. It will open anything and everything whereas I've had a couple of "could not open" errors from gedit this week. I also prefer Kate to Vscode.
Konsole by default switches tabs with ctrl tab but Terminal doesn't and thats basically my only issue with it.
Gnome seems to still require you to install a browser extension to use Shell Extensions.
KDE widgets are fantastic, I love having system monitors in a hidden panel at the top of my screen so I can really easily check system resource usage. I haven't found anything similar on Gnome yet.
KDE Connect is such a brilliant app, it wouldn't launch for me on Gnome but there is GSConnect for Gnome but its a 3rd party app
By default on KDE, if you shake your mouse the cursor gets bigger and there doesn't seem to be a size limit which is so fun to do lol
Going from Plasma 5 to 6 was a nightmare for me but its probably because I was using EndeavourOS so the updates were sooner and more frequent.
Overall I think Gnome looks and feels a bit outdated and clunky and KDE looks and feels more modern with better integration across apps but that might just be QT vs GTK
I do plan on continuing to use Gnome for at least another 2 months to give it a fair try but I will almost always recommended KDE because I prefer the look and feel