Well, one thing that makes police officers and soldiers go back to the M1911 is the fact that the .45ACP caliber is judged to be more effective than anything else, with a good balance between recoil, accuracy and stopping power. It's heavy and fast enough to knock down any target - with the help of a hollow-tip or not. The M1911 is also "thin" enough for concealed carry, whereas double-stack magazines create more noticeable bulges (I dunno about the Para-Ordnance P14-45, though) that are not always appreciated by plainclothes agents.
I believe .45ACP is also the caliber that can trigger
hydrostatic shock the best, which is no small advantage when you are in the field and want a target to go down, either right upon impact...or later.