Not going to join the overall debate, just going to tell you my own experience and feelings on the matter.
I have a long history with wheelguns and a strong preference for the .357 Magnum round. Tried various .44 Magnums, never could shoot 'em worth a damn and went back to .357 (and .38's for fun).
Got introduced to the Springfield "XD" line all at once with an XD-9, and XD-40, and an XD-45 (all in 4" service configuration).
Firing the XD-9 I was very accurate. Perceived recoil and noise level were very light. My only issue was it just felt like a pop-gun to me (being used to .357 loads).
Firing the XD-40 I was not nearly as accurate (initially) but my instinctive feeling was that it was ME, not the gun or round. Perceived recoil and noise level seemed a little high, much like a .357 load. Put simply, I took to this weapon and round like a duck takes to water.
Firing the XD-45 I was slightly more accurate than the 40, but not quite as accurate as the 9mm. Perceived recoil and noise level seemed (to my surprise) quite a bit lower than the XD-40. But somehow it felt, well, I guess "lethargic" would be the best word. I don't know if that makes any sense to anyone else but it's the best description I can come up with.
So I practice with, and soon will CCW the XD-40 not the 9mm or .45ACP. Why? I'm not sure I can quantify it, the .40 just struck a chord with me. A little practice led to decent mastery of the gun and the round and now I think I'd feel lost with something else. (I'm especially excited about getting an XD-40 compact now).
Disclaimer: Can't rightly comment on actual performance against a meat target though. Never shot anything but paper or plinkin' targets with any pistol and hope I never actually have to do so.