Guy Hebert in his prime was spectacular for the Ducks. He was probably top 10-15 in the game. I doubt Dunham was that good in his prime. However, I guess you can say that Dunham was more consistent throughout his career.
I found myself cursing at the TV more often when Mike 'Captain Rebound' Dunham was in goal, so I'd go with Guy Hebert. I don't understand how a goaltender could so consistently put a rebound perfectly onto the tape of an opposing player like Dunham did.