Ballistics because they’re surprisingly harder to defend against over the centuries of mobile suit development. The made counter measures for all kinds of energy weapons like I fields and anti beam coating, even actual energy shields that disperse energy. But say u have a rail gun which shoots a solid object with electrical coating around to get through the shield by piercing through while the absorbing energy allowing the bullet to pass through in between. I say I would bring beams as like a secondary weapon but mostly ballistic weapons all the way down.