what will be my next server operating system (Fedora Server, Fedora CoreOS, NixOS), your experience and opinion

I want to reset my server soon and I'm toying with the idea of using a different operating system. I am currently using Ubuntu Server LTS. However, I have been toying with the idea of using Fedora Server (I use Fedora on my laptop and made good experiences with it) or even Fedora CoreOS. I also recently installed NixOS on my...