Over the years, I've had to work with various text editors. I just don't like having to learn new programs that do the same thing as old ones. If I'd learned vi first, I might not have wanted to learn Emacs.

Emacs has a number of features that I use a lot. I don't know if vi has them.

1. It's programmable. When it's running, a LISP interpreter is running. It's possible to program your own functions using Emacs-Lisp and over the years I've written a lot of functions.

2. It has modes for different types of files, so the key settings are different depending on what sort of file you're editing. There's an HTML mode, a C mode, a FORTRAN mode, a TeX mode, etc.

3. It has abbreviations, so, for example, I can type "prgrm" and when I type a space or a punctuation mark it expands into "program". I have dozens of abbreviations, which are defined per mode.

4. I can open a shell in a separate window.

5. You can store text in registers and insert it, so it's like copying and pasting with the mouse, except you can save multiple blocks of text.

6. The rectangle editing feature is very nice. That is, you can manipulate rectangular blocks within a text. That's handy for indentation, but also for other things.

Emacs has lots of other features, many of which I don't use, some which I may well use someday.