RE: 9mm, .40 , .45
If you get the XD 4" .40, you wont be disappointed. There's something about the .40 that makes it deadlier than a .45. A DEA agent I know told me it was something about the motion of air surrounding the flying bullet that did even more tissue damage at the POI. Don't quote me on that one though. Recoil with the XD is a non-issue anyway.