Goku can thus use Super Saiyan with almost no effort, reserving a switch to Super Saiyan 2 only for the most important moments, a similar strategy to what Vegeta will adopt in Dragon Ball Super ...
In Dragon Ball Z: Battle of Gods, SSJ2 Vegeta briefly surpasses ... they're emotional. Goku turning Super Saiyan on Namek is an emotionally charged moment that's been building up all arc.