Could it possibly be because you prefer 9mm over .45?
I actually like the "torque" feel of a .45 best, and I thought 9mm felt a little boring at first. I think it has more to do with really liking the gun. Then again, other plastic 9mms I've shot didn't seem to have any character to me. I like all my guns, and on any given day, I will prefer one over the other, but usually it's between my HK and my SIG. My reasoning for preference is unquantifiable.