In my large frame Ruger Blackhawk "Liberty" Model convertible, the .45 Colt cylinder is more accurate at a greater distance, but only if strong handloads are used.
The accuracy of my Mdl. 97 FA .45 convertible is approximately equal for both cylinders, with a slight edge to the .45 Colt at say 25 yards, but once again, as the distance increases, the .45 Colt becomes more accurate with 1100+ fps handloads.
My new Ruger Flattop .45 convertible is more accurate with the ACP cylinder than with the .45 Colt. Since it's built on the mid-frame (.357 size) I haven't loaded heavy .45 Colt loads, and won't, so I expect the ACP cylinder to remain the most accurate.
Finally, I just acquired a Ruger mid-frame Birdshead New Vaquero in .45 ACP only. It is just as accurate as the Flattop with the ACP cylinder.
In other words, I have found the .45 Colt cylinder to be more accurate close and at the longer distances only if heavier than standard loads are used (1100-1200 + fps vs 825-850 fps) in my guns.
Since you have no interest in hand loading, I suspect that you will probably be adequately satisfied with an ACP cylinder. Yes, the ACP cylinders were an afterthought in single actions, BUT ... yes they can be quite useful and fun. UNLESS, as Lloyd points out, you get one with minute of barn door accuracy. Of course, that can happen with any caliber.
I'm satisfied enough that none of mine are for sale, if that helps in the decision making.