I think Goku is clearly the more powerful. But the X factor here is that Goku is...... kind-of a dope.
Not that Superman is known for his towering intellect but if he did something like say "Your shoes untied." or "Hey, what's that behind you!" in the middle of the fight Goku would probably be dumb enough to fall for it.....multiple times. So, though i think the smart money is on Goku, it's not like there are no chinks in his armor.