Not to start an argument, but who are these law enforcement agencies buying the XDs? I am not in that line of work any longer but do try to keep up with the latest developments and I have not heard of a single law enforcement officer or agency buying or using the XDs. As a matter of fact, most consider it a second rate sidearm and to be yet another Glock knock-off. The reason I ask is that I have seen this claim before but yet, no one seems to know who these cops are using XDs. I don't personally know enough about them (XDs) to have an opinion on whether or not they deserve consideration as a valid duty weapon choice.
Reality is, no matter how much some don't want it to be true, that Glock dominates the American law enforcement market. The figure of 65-75% is right on. I base this on personal observations instructing recruits at a law enforcement academy in addition to training police officers at several departments.
If some sort of research project was conducted, I believe it would show Glock as being the most used sidearm, followed by Sig Sauer and perhaps Heckler und Koch. The Beretta is also still in wide use, as are Smith & Wessons in many Sheriff's offices due to some sort of "buy American" deal or agreement that many elected sheriffs have entered into.
In addition to being a great choice for law enforcement use, Glock offers a quality product at a much lower price than the other companies. Many a young (or old I suppose) recruit will pick a $400 Glock over a $600-800 Sig or H&K most of the time for no other reason than economics. If those other companies were to offer deep discounts to LE, they would probably pick up more of the market.
Anyway, I am off my soap box.