...and the premise of the character specifically. When you're dealing with a Hitler worshiping carrier pigeon keeper, there's little room for subtlety.
Ferrell's a funny guy, but better in small doses. Carrey just makes funny faces. Ferrel > Carrey. If we're looking for an Unfunny Battle Royale of popular comedians, I'd pit Carrey against Dane Cook. Or how about "Larry the Cable Guy"?