M&S were two former LEO's that tried to quantify something that many talked about but had never bothered to actually study.
The M&S works are valuable in the sense that many can along to decry them but few would bother to try to come up with better information. They tried to compile the available information from actual documented shootings and make something useful out of it.
The noisiest critic was Maarten van Maanen of the now defunct International Wound Ballistics Association. See Section 71
Strangely, members of the IWBA were generally from the camp knows as Jello Junkies.