Interesting thread on the 9mm/38S calibers conversions.
I have done one conversion from 9mm TO 38S with just a barrel, recoil spring and extractor change. I did have to open up the breech face just a tad on that one. Another conversion on a Kimber Eclipse 38S TO 9mm, just a barrel and a recoil spring, both of them will feed anything I put in them, all my reloads BTW.
I Have also converted a Rock Island 45 to a 40mm with only a barrel, nothing else, I never cared for the 40S&W until I shot it in a 5" 1911. Really tames it down. I think the Rock Islands are the International Harvester of 1911's, You just can't hurt them and they just keep on working. Like an old Scout, Not pretty, but a work horse and dependable
As to the Caliber issue I like all the above. 9mm,38Super 45. I have been lucky I guess having no real issues with feeding on any of them.
I have a Colt Gov'mt competition 9mm and it is a dream, shoots better than I do, and a Gold cup that is just a tack driver in 45. Great guns, all of them. I shoot what works for me and performs. Colt, Springfield, S&W, Rock Island, I like them all. If it's a 1911, I like it, regardless of caliber