When comparing GNU Guix vs Puppy Linux, the Slant community recommends Puppy Linux for most people. In the question“What are the best Linux distributions for desktops?” Puppy Linux is ranked 14th while GNU Guix is ranked 82nd. The most important reason people chose Puppy Linux is:
Puppy Linux requires 128MB of RAM and 333Mhz of CPU, although 256MB of RAM is recommended.
Specs
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Pros
Pro Can setup a shell which has exactly the defined libraries available
A method which works across languages and provides a reproducible programming environment.
Pro Can always roll back to a safe state
Guix creates new profile generations for each operation. If anything goes wrong, a simple --roll-back gets you immediately back to the previous, working, generation. Because it is a purely functional package management system, generations don't affect each other, so you're back to the exact same state as before : still working.
Pro Can create independent packages
Guix pack creates packages which do not need Guix to be run.
Pro No side effects when building packages
Guix is a purely functional package management system. This means that the act of building a package does not have side effects, such as destructively updating or deleting files that may be used by other packages.
Pro Can build containers right-away, from docker to tarballs
See guix pack --help and here.
Pro Easy to add your own packages
The clean and declarative syntax makes it easy to define new packages by using an existing one as an example.
Pro Doesn't require root privileges
Normal users can install packages on a Guix-enabled system, or even run their own Guix instance if the system isn't Guix-enabled.
Pro Extremely low minimum system requirements
Puppy Linux requires 128MB of RAM and 333Mhz of CPU, although 256MB of RAM is recommended.
Pro The whole OS runs off of RAM
Since Puppy Linux is completely loaded and run off of RAM instead of HDD, it's read/write speed is not a factor.
Pro Designed to run as a live USB/CD
A portable version, that can be carried on a thumb drive without requiring installation, weighs less than 100MB; a Live CD - less than 150MB. You can even save your settings and files for Puppy on the external device/media.
Running off a live CD also has security benefits, as your system will reset to the known config after each boot.
Pro Different distro based versions available
Puppy Linux offers a few different releases.
The first is an Ubuntu based release called Tahrpup, by using this version the user is able to take advantage of all software and support from Ubuntu.
The second version is called Slacko, which is built upon the Slackware binaries.
The third is called Wary and it is built to support older hardware than the rest.
And the fourth is called Quirky, which is used as a base to explore new ideas.
Pro Linux distro designed for this exact purpose
Pro Offers a long term support release
Puppy Linux offers an LTS release called Precise.
Pro It can be the only distro that works
Sometimes, Puppy Linux is the only distro that works on an old machine: all other distros are more demanding.
Pro JWM used as window manager
JWM is a low resource window manager that is used in most Puppy Linux installs.
Cons
Con Updates take a long time
It's gotten better over time but both updating Guix itself and updating the installed packages can take a long time.
Con Cannot handle filetypes that have different semantics across different versions
While the functional approach that Guix takes is great for sandboxing binary artifacts of packages, it seriously lacks any power in handling configuration files or user data. It's difficult to upgrade and downgrade files where semantics and syntax can change between versions.
Con A bit ugly
Using puppy makes you feel like you just jumped 20 years into the past. Being that the purpose of Puppy Linux is to run or really low resource machines the software used is often on the older side, which is precisely why it has a 20 year old look.

Con Not as light as it used to be
It's light, but not as light as it was 1-2 years ago.
Con Smallest software library ever
You can barely find any precompiled packages for Puppy.
Con No built in compositing
Being a low resource distro there is zero built in compositing for the JWM window manager. Though one can be added through a bit of work.
