When comparing Research Unix vs NixOS, the Slant community recommends NixOS for most people. In the question“What are the best operating systems for advanced users?” NixOS is ranked 8th while Research Unix is ranked 30th. The most important reason people chose NixOS is:
Atomic non-destructive upgrades / rollback of a system upgrade / declarative reproducible system configuration / unprivileged installation of packages / transparent source or binary deployment.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro BSD are based on Unix
Pro State of the art package manager
Atomic non-destructive upgrades / rollback of a system upgrade / declarative reproducible system configuration / unprivileged installation of packages / transparent source or binary deployment.
Pro Minimal
You can start with a minimal environment and add packages and software to suit your needs as you go along.
Pro Reproducible system
NixOS is configured using the Nix package manager, allowing your system to be replicated and kept in sync across multiple machines. Great for keeping a laptop and desktop in sync.
Pro Robust
Packages don't break after a NixOS upgrade as they are prone to with other distros (especially Arch).
Cons
Con Discontinued in 1992
Con You can't get UNIX anymore
Con Documentation is not good
A lot of the documentation of various functions is buried on the source code, their respective manuals, or non-existent. The documentation, the conventions, and the scattered toolchain really made searching for stuff easily missable.