Who was the better trainer? Who was more integral in Goku's success?
Goku kept using the Kamehameha
They're both throwaway characters learning Goku new moves to beat the nemesis du jour. The difference is that the Kamehameha was convenient to keep using over and over whereas Kaiokan was invalidaded by Super Saiyan golden shower transformations.
Roshi barely taught him anything. He just made Goku run around doing work and wear a heavy shell.
Popo was Goku's most important teacher because he actually taught him how to fight correctly.
Nah, Princess Snake was his best "training", if you know what I mean...
He used what he learned from ChiChi tho.
The lazer was the best trainer because it made goku learn not to turn off your "defence" like a bitch.