you don't need to be super strong to destroy the sun, Rohsi shot the moon down and he has around 100 (whatever powerlevel measures are called), even considering it was Dragon Ball and not Dragon Ball Z. taking out the sun shouldn't take more than 10000 units of whatever.
still, Superman wins.
supes can survive some minutes without the sun present, and can travel to different solar systems. Goku needs a working eco-system to survive in. goku can theoretically destroy every non red sun and start living there, but it doesn't fit him to do so.

about superman going off the rails after being hit by a train...
a. if he took it at full force, the train would evaporate, killing anyone onboard and go through nuclear fusion.
b. two can play at that game. Goku needed to go supersaiyan to lift a bus at one time (episode 110, probably based on the superhero genre conventions).

Superman wins because he can't lose. Goku loses alot, and that's why he sometimes wins.