Well even in same game. The character each have their own advantage. Like in megaman serie. Let's just look at 3 quickly.
Megaman X, Zero and Bass. They are all reploid with similar capacity but personal advantage.
Megaman is basicly a ranged unit that move lot.

Zero is mostly a Melee unit with some range attack but he is melee and move lot.

Bass is mostly a *turret* really. He cant move while shooting unless the movement is by jump or he is transformed with his dog(I dont remember the name) His buster is shooting very quick and his special attack he get from boss are mostly made to make his *turret* position stronger.