These tags all seem to refer to the same things, and people are using all of them interchangeably.  Personally, I'd have picked the one that nobody seems to have gone for -- [virtual-host] -- but I guess I'm out of touch with today's urban sysadmin.  I don't have any other preference, but whichever one the mods choose, I'll commit to writing a tag wiki for it.

As an aside, if you stare at the tag search page for 'virtual', the word starts lose all meaning eventually...