Myself, I prefer Emacs, because I like it's base philosophy (everything is a text-buffer, everything is hackable LISP) and the endless possibilities that provides in form of customization, extensions (and extension on extensions, and customization of those, etc etc).
I don't think Atom is quite there, or ever will be. It will be interesting to see if if has the staying power of Emacs, or if it will yet another TextMate, Sublime Text or whatever hip text-editor of the month there has been the last decade.