To expand on the previous response a bit: Cranks can have different offsets of chainrings and arms relative to the spindle hole. Those are chosen by considering the engineering implications of those offsets, along with frame clearances, ankle clearance, and chainline. Why some companies choose one package of offsets or another is a complicated question that has to do with the above, plus manufacturing, materials, aesthetics, etc. Pretty hard to cover in a forum post.