Arch is really great, but using the system now for ~5 years I cannot remember where every configuration is, which packages are installed and why, and things just get messy. I'm sure that some issues the system has are do to things I screwed up along the way, and these will be solved if I just reinstall. But with NixOS it feels so easy to find what changes you've done to the system, to leave a comment saying why etc. It feels to me much more maintainable.