Fit and function.
The grip angles of the pistols you mention are different. I'd suggest you borrow or rent one of each, and see which feels best for you. All 1911's will have the same grip angle, a Sig will have the same angle as another Sig, etc. The P226 is a fullsize pistol, the 1911 is slimmer. But it might not point well for you while the Sig may feel like magic. The XD has a similar grip angle to a 1911 with more capacity, but it's not as thin.
There's a hundred things that go into the decision. Caliber, action, fit, ease of concealment, ease of draw from concealment, how and where to carry reloads, how much to modify dress to conceal, the list goes on.