Goku for sure. Superman tends to win fights because he's strong, not because he knows how to fight properly. Take away all the super powers and goku would destroy superman in hand to hand combat. Give back the powers snd goku far outranks the man of steel.
As for your kryptonite from the dragon theory, I don't think goku would ever stoop to such a low measure. It would be s last resort if sm was trying to blow up the planet or something, but that's not exactly superman s thing lol. Goku always says he prefers to fight enemies at thier strongest. He is a saiyin after all.
//dbzfangirlherehi