>>58714355Alphas have bigger hitboxes and are easier to notice in a hectic situation, but the hurtboxes on their attacks are also larger.
A tank that's going to charge into the fray and start spamming AoE moves like Earthquake or make heavy usage of movies with lots of i-frames might benefit from being bigger, but a ranged attacker who wants to sneak up and Ice Beam opponents who aren't paying attention prefers to be small and harder to notice.
Note that this only applies to PVP, size is pretty much meaningless during solo play.
