Anyone check out the comparison tool on Winchesters website? http://www.winchester.com/SiteCollectionDocuments/flash-SWFs/law_bullit.swf It looks to me that the 9mm performs as good if not better than the 40 cal through Denim and heavy cloth. It expands just as well and sometimes more and doesn't over penetrate where the 40 cal might. Is my assessment correct? Also I am not saying that the 9mm is a better self defense round. It just looks like if you use Winchester Bonded Rangers, it may be. Keep in mind I am by far no expert in what is/isn't a good defense round.