For me, it was the realization that emacs can be configured to do anything you want. If you don't like how it works (and you probably won't), you can change it. Do you wish that Alt-<left arrow> would delete all of the whitespace in front of your cursor and translate the rest of the line to piglatin? You can to that. Do you want to send a copy of your file to an ftp site in addition to your local disk when you hit 'save'? And also push to github? Go for it. I guess you could say that you get out of it what you put into it. I sometimes find the auto-complete in emacs a bit lacking and I'll try another editor/IDE, but once I find something I don't like and I can't change it, I'll go back.
That being said, I think you're probably right that it is better in general and other tools can be better in specific situations.