SRP76

Gohan's a guy who's goal in life is to be a scientist, remember? He's not a fighter. Yamcha is; that's what he does. Beats on people and steals their money and capsules.

Gohan was also said to have stopped working out; Yamcha simply was not.

And Gohan also didn't have a villain hanging over him like a dark cloud, and Yamcha and the crew did at that time. Piccolo's not exactly Santa Claus, you know.