Well ... emacs is a very extensible editor, and people have done
so for quite a few years now. The result is that it can do pretty
much anything (I'm not sure it brews coffee).Some people joke
that emacs is a great operating system, but that it's a pity that
there's no decent editor for it.
Personally I use emacs where ever I can (no, not for mail or as
a news reader or browser) for editing purposes.
Vi ... vi just is. It's pretty much in every distro, even though
the flavours vary. One should learn the basics of vi for emergency
situations, some people even swear by it for everyday work.
Vim makes it vi a bit more bearable (if you're into that kind of
thing ;}) ...