Yes, but if Saitama defeated Goku with one punch, he’d just get resurrected with the dragon balls, get an extreme power boost from being a Sayain and dying, and then probably train with God or something to defeat Saitama in a rematch at the Interdimensional Martial Arts Tournament.

Saitama may be the stronger of the two but Goku has plot armor for decades.

But you forget Saitama is a Gag character in part who's main gag also gives him powerful plot armour, it would be a class of rival plot armours.