By economic im sure that you mean diplomatic..^^
Early Warmongering civs benefit because unit movement doesn't scale with game speed. So where it normally takes a couple centuries for your army to cross a continent and attack your rival, on Marathon it'll only take a couple decades. Thus, more turns of warring per era and more time to use particular units before they're obsolete.
I imagine, off the top of my head, the Huns, Rome, and Greece would be especially good since they each have 2 early game UUs.
(I've enjoyed playing standard speed and employing real strategy so much, I'm almost embarrassed it took me so long to switch. I will say that I think it could be a bit more balanced so that we have about 30-40% more time for warfare in the earlier ages ..various early windows of advantage don't seem to last quite long enough unless you time it perfectly).
Well, there's always the middle ground: Epic speed.