If you ever wonder what vim is capable of, the question is not "Can vim do this?" The question is "How can I configure vim to do this?" Because 99% of the time vim can do it, and you are just a google search away from making vim meet your needs.
Installing Atom adds two command line commands - atom and apm. The first one runs the application itself and the second one is the Atom Package Manager that's used to add and remove various components from the package listing. While these features can be set up with other editors as well, Atom...
The number of available plugins is limited. As far as I know, plugins need to be written in C++ which could be somewhat of a barrier for third party developers with the need to extend the core product.
Customizations can be made to a wide range of Emacs' functions through a Lisp dialect. A robust list of existing Lisp extensions include the practical (git integration, syntax highlighting, etc) to the utilitarian (calculators, calendars) to the sublime (chess, Eliza).