Based on the situation, I'm guessing that the no powers clause means that everything is dismissed except for their durability, strength, and resourcefulness.
If this is the deal Superman wins this due to durability issues, regardless of whether or not Thor is stronger, and a better fighter, Superman can take better than he can give, and Thor simply can't generate enough force with his fists alone to put Superman down for very long.
Superman however has the strength, endurance, and durability to outlast, and put Thor down. It would take a while but eventually Thor would be the one to fall. Superman would be injured due to Thor's superior H2H knowledge so this would not be as one sided as many may think.