For me, the factors were:
And from what I hear, the main selling point of NixOS is how easy it is to reinstall.
Well, that isn’t the first thing I’d mention, but whatever. Use whatever you’re comfortable with.
Did you try Nix (on Arch) or NixOS? For the latter, https://nixos.org/manual/nixos/stable/#sec-declarative-package-mgmt explains the basic installation.
Honestly at this point that’d be a detriment