The biggest thing vim has over nano (and other CLI text editors I've used) is its lack of persistent control / nav bar. You have the entire terminal window at your disposal for editing, which I really appreciate. The common bash on vim is not knowing its commands, but once you learn how to enter INSERT mode, save, and quit, what else do you really need?

I like the key bindings that allow for quick and efficient manipulation of my code. I find it very convenient that you can use vim to easily read and modify files without leaving the terminal.

Simple, fast and after you learn you be higly productive.