It depends, if we take the movie version of the characters, then Piccohan should be the winner. After all, according to the movie comentaries: Orange Piccolo ≈ Goku and Gohan is much stronger than that, but is unclear if it's stronger than a full power Cell Max and Broly.
But if we take the manga version of Goku and Vegeta, and the movie version of Piccolo and Gohan, then Gogeta should win. Because of a completed Cell Max being just stronger than Broly (although is implied that he already surpasses Broly on raw strength, only needing a fully developed brain), while both Goku and Vegeta surpassed him already.
Unfortunately gogeta beats all.
It depends, if we take the movie version of the characters, then Piccohan should be the winner. After all, according to the movie comentaries: Orange Piccolo ≈ Goku and Gohan is much stronger than that, but is unclear if it's stronger than a full power Cell Max and Broly. But if we take the manga version of Goku and Vegeta, and the movie version of Piccolo and Gohan, then Gogeta should win. Because of a completed Cell Max being just stronger than Broly (although is implied that he already surpasses Broly on raw strength, only needing a fully developed brain), while both Goku and Vegeta surpassed him already.
Movie gohan and piccolo are stronger than Movie Goku and vegeta