Hmmm..
At first I put in "Everyone Equally" on this one, but now that I think about it I should have put "The Players". Not that the GM shouldn't have fun...he/she should. But I think the Players should be the beneficiaries.
This is becuase the games are really for the players to triumph (or resist in a CoC game) against the adversaries against them. And who are the adversaries that get stomped, smashed, outsmarted, cajun-fried and evaded? That would be the DM's people.
The DM is setup to fail. Oh sure, he can make things challenging, maybe even score a few TPKs here and there. But at the end of the day the DM has to lose, and losing can diminish the fun a tiny bit.
Personally I like DMing. It's a lot of fun, but I always see it as creating a story for my players, and as such that means they will probably triumph and my devious monsters, well-crafted traps and insidious plots that I spent all that time on must fall. So be it.
Anyways, that's my 2 coppers