Differences between the XD and XDM: - Match grade barrel on the M - The M's have interchangeable back straps; change them out to fit your hand - The M's have a different pattern on the grip - Higher capacity in the M magazines - The M's have a different trigger system (they call it "minimal reset trigger", or MRT), supposed to be better on follow-up shots - .40 & .45 M's have a 4.5" barrel, the XD is available in 3" sub compact (9mm and .40), 4" (compact, service, tactical) in 9mm, .40, .357, and .45 ACP/GAP, and 5" in 9mm, .40, .357, and .45 Both the XD and XDM have: - Grip safety - Trigger safety - Striker status indicator - Loaded chamber indicator I have the XD in 9mm and .45 ACP, the .45 has a thumb safety, both very reliable and accurate.