I think functional distros like Guix or Nix are just another thing. Their ability of programming , provisioning and deploying software environments is unparalleled. My personal favorite is Guix since, while having less packages than Nix, it has the most consistent experience: everything is in Scheme from the top to the bottom of the distro. Also it pushes really hard on a sane bootstrapping story while allowing for impurity through channels like nonguix .
The main downside is the lack of tutorials and a documentation that’s very intense, let’s say. typical of GNU projects. I suggest the System Crafters youtube channel which has a lot of nice tutorials
They do very different things even if the outcome is the same. You are not rollingback your system by downgrading each package. You are statefully changing your filesystem. Rollbacks in Nix and Guix are internet free, atomic and reproducible because they amount to changing the target of a single symlink