Dragon Ball fans love to ask one type of question — who is the strongest? The answer generally changes as the characters gain new power-ups or meet powerful new enemies. As such, the strongest character constantly changes as the story progresses. Saiyans, for example, have commonly been weighed against each other based on who has attained the highest level of Super Saiyan. However, if two Saiyans have achieved the same level, this assessment doesn't matter. When figuring out which Saiyan is stronger, it would be best to measure their performance when they're in the same form, like Super Saiyan.
Source：https://www.cbr.com/dragon-ball-strongest-super-saiyan/
