The .45 ACP cartridge is accurate and easy to reload, and the Colt pistol is a natural pointer, accurate, easy to strip and clean, and impossible to destroy. It can be left in its natural "rattle trap" military state so that it will fire even if doused in mud, or it can be fine-tuned and tightened up to superior accuracy (at the cost of some reliability), and just about any level in between. When tuned up, there is no better large caliber target pistol (I competed with one of mine for several years), but I understand a lot of the combat pistolero crowd have gone to the DA pistols since my time. If you prefer a DA, I tried the Sig and the Glock but preferred the Sig.
I am not a fan of 9mm, never have been since my WWII vet dad told me that he saw a number of American GIs in N. Africa and Italy merely wounded by the 9mm Lugers and Walthers, not necessarily dangerous wounds either . . . but he never saw a live German with a .45 hole in him. To be absolutely accurate, this could have been because any German able to ambulate was leaving the vicinity as fast as he could hobble, but I don't think so. . . . Besides, the tapered case on the 9mm makes it a bear to reload.