Yeah, but ya know.... even while being such a simplistic game, there are a few details that called my attention... like.... that staff/book magic tipes are more bulky than gun ones, but have less attack or speed. That would make a slight difference while thinking how do you want your squad to be. I dont know if there is a similar case on the other types of girls.
Anyway, in the end this is mainly a wifu collecting game so just throw the units you like the most.