Move from shoulder to rifle as the tech was advanced and weight reduced. Example being say a modern laptop compared to say, this thing.
I don't think it says, but I'd rather have a heavy handle weapon over a rifle/shoulder weapon. There aren't enough handle weapons, and that form factor, like the plasma caster, seems to fit better for the type of weapon, especially a prototype. A reload like the minigun makes sense, with a large power pack and ammo unit to swap out.

