The AUR has more eyes on it though and can be more up to date. Getting OBS plugins "wrapped" was a pain in the ass in NixOS and they were out of date. But I'll admit it's a pretty niche example.
Yeah I was on unstable. This was a few months ago and the plugin was obs-backgroundremoval which was several versions out of date and missing out on a CPU core restriction feature that I needed. The maintainer actually had updated the package in his personal repo but it hadn't been pushed to nixpkgs unstable because it was waiting on some graphics library that hadn't been updated. I'm a huge Nixos noob and no matter how I tried to install the package from the maintainer's repo I couldn't get it installed or properly wrapped and the documentation sucked. I spent several days trying to resolve the issue.
I installed Endeavouros, ran yay -S obs-backgroundremoval and boom installed, latest version, no problems.
Don't get me wrong I actually love the ideas behind Nixos and I've tried to run it as my daily driver a few times now but I always seem to run into some problem. I'm more than happy to chalk it up to skill issue. This is my daily driver though that I use for school. It doesn't necessarily need to be stable but I need it to work and I need to understand it.
That's basically just some software is not up to date. I did the pull request to package it myself, it wasn't so difficult. The best part is I used an overlay so I could run it and use it while the pull request was being commented on