The rimless round is a recent development and has a different name, which I forget. Don't know if it is reliable in an original .38 Super or if it needs a new barrel. Starline makes brass for it, as well as the original, and also brass marked. "Super .38 +P+" which seems the same as their regular .38 Super but is perhaps meant to mark users hot handloads as too hot for an original Colt.
I've fired many .38 Super 1911s and own a Commander-sized Llama in that caliber. Llamas vary a LOT in quality, but mine has been extremely reliable for many years and thousands of rounds. It was made in the early 1970s and imported by Stoegers. I've found that the best Llamas are those with a solid rib on the barrel; the later ones with a "ventilated" rib are less reliable.
The only advantage to the .38 Super for most non-USPSA users, IMO, is that it is a better hunting round at longer ranges than the .45 ACP. If you were to want it for varmint or small game hunting, or shooting deer at woods distances from a tree stand, I'd choose it over the .45. Otherwise, as already stated, it's main advantage is it is legal in some countries where the .45 Automatic is barred because of being a "military" caliber.
And it is fun to shoot at longer distances.