One distinguishing feature is their optional install strategy: running packages directly from compressed archives instead of unpacking them into node_modules.

https://yarnpkg.com/features/pnp

Very similar to using .jar's in Java instead of directory trees of .class files.

It's somewhat hacky though, and editor/tool support varies.

- since there are far fewer small files, it can be faster especially on Windows if you're forced to work on it for some reason

- the archives can be stored into the git repository (through git-lfs or friends), removing dependency on the internet and the package registry