The accuracy in the .45 convertible is about the same with .45 colt and .45 ACP. I think I'd give a very slight edge to the .45 colt, but you can hardly tell the difference. The .357/9mm is a different story. There is a noticeable accuracy difference. You can get the 9mm reasonably accurate by going to hotter loads with lead bullets, relatively softer lead bullets or by loading .38 special rounds into the 9mm cases. I have both the .45 and .357 convertibles. I shoot a fair amount of .45 ACP but not much 9mm. It's just too much trouble to get the "right" 9mm round. If you reload, there isn't that much savings in shooting 9mm versus .38 special or .357 mag.
The only thing I didn't like about my .45 convertible was the rubber grips. I swapped the rosewood grips from my single six. They do better on the single six, but will be eventually replaced with better grips.