Regular armor, I'd give the edge to Wondy, especially in his later ionic form, but victory wouldn't be out of Iron Man's reach. Wonder Man 7/10
Pre-extremis armor where every writer seemed to be making him weaker and weaker, Wonder Man would win in all instances.
Extremis Iron Man, by all showings so far would probably be about an even split, maybe even Iron Man going 6/10 or so. Maybe I just overrate Wonder Man. If Iron Man do the remote call on his old armors, then Wondy's toast every time.
I agree with Scarlet Spider. Regular average middle tier armor, Wonder Man 7 out of 10.
With the Extremis Armor and access to all his other armors, equals an ass kicking for Wonder Man. Wonder Man has trouble with one Iron Man, an army of them would literally stomp him.