When comparing NixOS vs SliTaz, the Slant community recommends SliTaz for most people. In the question“What are the best Linux distributions for an old machine?” SliTaz is ranked 19th while NixOS is ranked 30th.
Ranked in these QuestionsQuestion Ranking
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 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.
I have never had a package break on me after a NixOS upgrade as I have with other distros (especially Arch).
You can start with a minimal environment and add packages and software to suit your needs as you go along.
Pro Very fast
Pro Can add desktop effects
SliTaz has a feature called "Desktop Effects" which can add shadow or fade effects to windows.
Pro Very customizable
SliTaz is very customizable. You can programatically edit and change anything you want on how the OS looks or behaves.
Pro One of the smallest distributions with desktop GUI
The core liveCD is only 35 megabytes. The boot-from-internet option fits on a floppy.
Con Documentation is not good
Con A configuration change might end up bricking your system
Con Uses a text-based installer
Con Install instructions are in French
When first booting SliTaz from a USB or from a Live CD, the installation instructions are in French.
Con Not much variety as to available applications
SliTaz does not have as many applications in its repositories as the bigger distros such as Ubuntu.