Correct me if I'm wrong, but Mid length slows down the cycle rate slightly (you'll never notice a difference, like hundreds of a second) and is overall less pressure which results in less wear and tear in the long run. Also I think another reason people buy them is because they have slightly less recoil? I've always read mid length is better, so that's what I bought, and I love it. I feel like when I shoot my Dad's, it's got more recoil (there's not much at all to start with) and overall seems more like it's designed for fully auto or burst. Mid length seems the right pace to me. This may be incorrect, just my thoughts, so someone please correct me if I'm wrong.