> The other thing is package availability: it's amazing on Nix. Plus, they remain relatively fresh on the unstable channel. How's that on Guix?

The article says it seemed good. If you want a quantified look, Repology has some stats.

GNU Guix: https://repology.org/repository/gnuguix

Nixpkgs unstable: https://repology.org/repository/nix_unstable

However, note that the Guix entry doesn't include Nonguix AFAICT. So, it's a bit higher if you are using nonguix.

Unfortunately, some packages which are free software can only be found in nonguix, due to Guix wanting to be able to build everything from source. So things like Gradle that require a huge bootstrap chain that no one yet has bothered to do are instead packaged in nonguix as a binary download.