The .45 ACP should NEVER be confused with, nor erroneously equilibrated with the .45 Colt if one is talking anything beyond factory ballistics. The reason is because when handloaded the .45 Colt moves into the .44 Magnum class with ease.
The choice between .44 Magnum and .45 Colt in ANY handgun really boils down to whether the user is handloading or not. For the handloader the .45 Colt is the way to go hands down because it will sling a bigger, heavier slug at "equal" velocity with lower pounds per square inch chamber pressure. Of course handloaders already know all this.
IF I were planning to rely on factory ammo I'd probably opt for the .44 Mag, though it is worth knowing that once can now choose heavily loaded .45 factory ammo so even someone welded to buying their ammo might still choose the .45 Colt caliber.
Of course the "right" answer might be to search out a S&W .460 because it can digest everything in .45 caliber from mild to wild with ease!