Place your bets in one corner we have the Action Ace, the Man of Steel, SUPERMAN and in the other, we have the Avenging Son, the Deep Sea Dynamo, the SUB-MARINER!! Who comes up on top in 1939?
Remember, Superman is not all-powerful here. He has limits, no heat vision, can be knocked down by heavy artillery and may not even be properly flying at this point.
And Namor is just as strong and bullet-proof and can fly. And has a mean streak.
Had it come to blows in 1939, which one is victorious??
We all know the answer: The winner is whoever the writer decides is the winner.
For my part, I can't really decide. Subby would probably fight dirtier, but he's impulsive and apt to make mistakes. Superman's a good brawler, but not as versatile (God help him if Subby gets him in the water). I guess I lean to Superman, who's strong enough to stay unbeaten long enough to come up with a plan.