I've shot a pair of XDm .45s, and before I tell you my take, here's how I came by them. I had just shot my XDm .40 and was having issues with the sights - the gun was shooting low and left. A guy came into the range and I told him my issues, and he let me borrow his .45 - it shot like a dream. I had night sights installed, and now my .40 shoots true. This was almost a year ago.
The other day, I was at the range, and I rented their XDM .45. The front of this gun was white, which I assume was just wear on the gun from many repeated firings. It only felt okay, but not great like I remembered, and it, too, was shooting low and right. The XDM also failed to fire on one round - the striker didn't even hit the primer. The glock that I tried that day shot true, I know it's older than the XDM, and it worked flawlessly.
Overall, I'd say the XDm would be a good choice under three conditions: 1) you don't trust the sights from the factory, and either resight it or install new sights. 2) you perform regular maintenance on it (clean/lube it after going to the range, just the basic stuff you would do to any other firearm, nothing excessive). 3) you don't abuse it like a range rental. In comparison, my .40 has worked flawless.
With that said, I should say that range does favor the Glock over the XDm, so I wonder if it prompts them to take better care of the Glocks.