If Goku had saved Piccolo, the fight against Vegeta would have been the same, since Piccolo would have left
everything to Goku. When the gang comes back, Vegeta goes down easier and he dies because Piccolo isn't as
forgiving as Krillin.
Piccolo follows the gang to Namek and receives Guru's boost along with Krillin. The boost renders him equal to his
post King Kai self. Seeing Piccolo's recklessness in canon, I guess he does not wait for Goku and goes to challenge
Freeza instead. Everybody dies, Freeza does not get his wish, destroys Namek and leaves.
Goku finds no Namek to land and returns to Earth. Later, he dies of heart virus and Androids destroy the world.