vim is a handy editor, you simple type vim filename
to open the file, edit, save and close.
emacs is an "operating system" pretend to be an editor, you can eval
code to change its behavior, and extend it as you like. A mode
to receive/send email on emacs is like an email software on operating system.
When doing simple editing, for example, modify a config file, I use vim.
Otherwise, I never leave emacs.