Mac ships with their own posix subsystem, WSL allows you to install a bunch of popular flavours of linux on top of Windows. I personally run Arch Linux and have access to a lot more bleeding edge packages.
To clarify, Mac ships with a native Unix [1], derived from BSD, not a posix subsystem. It has its own init (launchd) and its own GUI, but most of it is a Unix.
Using Macports or homebrew gets you most of the packages that are available for the various Linuxes, GNU utilities etc.
