Both KDE and Gnome are stable. Anaconda works the same way for both of them, because that stuff doesn’t have anything to do with the DE.
It really depends on your preferences. KDE is easily customizaple and has a lot of features and UX improvements. But it can clutter quite easily: these options can be overwhelming.
GNOME follows a very strict workflou design that’s more similar to how phones work and helps an ADHD brain, like me to focus more. You can customize it, but you’ll do so at your own risk.
Best to try out both in a live system and do some things that emulate your day-to-day workflow. Then you can decide. And you can always change afterwards! If you have a separate home-partition, reinstalling a new DE/Distro is super trivial.