I find the consistency and configurability great, but for me the killer features were being able to write elisp and kbd-macros to accomplish tasks that (most?) other editors can’t.

Modern conveniences include magit (the best git [porcelain] I’ve ever used) and cider, but I’ve been using emacs for 30+ years now and feel like for all but the first 6 months, it’s been an increasing time-saver and powerful lever for me to use.