I think that the reason why they make the five person team is that It gives five different point of views. It helps you better understand what is going on. It depends on the perspective to decide if it is a good point of view or a bad one.Take BATTLE OF THE PLANETS and VOLTRON for example. Both have 5-people in their team and they both have super powers. But the only thing that is different between the two is that they all have different points of view. Five people show what is happening from their own perspectives.