Compared to Emacs Lisp it’s nuanced but compared to most other non-Lisps it’s very clear: you can connect your Emacs to the Lisp runtime and hack on the program

Compared to Emacs Lisp it’s nuanced but compared to most other non-Lisps it’s very clear: you can connect your Emacs to the Lisp runtime and hack on the program while it runs, which is great for an interactive environment like a window manager.