While I agree with the premise of you post I think you are leaving out a very important element that applies to both mechanical and fixed blade broadheads.

If your bow is not well tuned and your arrows are not hitting square you are going to have decreased penetration. I think this is where the ball often get dropped with Mech. broadheads, and it has nothing to do with the quality of the product. It is an education issue for bowhunters.

Joe Bowhunter that doesn't have much technical knowledge sites his bow in and shoots it all summer. He screws on a Muzzy or two and they hit way off of the field points. Too often the answer is to go buy a pack of Mech. heads because they will hit the same as his FP's. He isn't going to get the penetration he should because the arrow is not flying correctly and not hitting the animal square. Many guys have the same issue with a fixed blade because they never shoot them until hunting.

I think this accounts for a great deal of the penetration issues.