9-Ball, I understand your concern about having a retention device on a holster. If your doing competition shooting you want to have a quick draw and not be fumbluing with a button or snap or anything else to get the gun out of the holster. Although if you practice alot, I dont think a button or snap will slow you down much. Still, I think you are on the right track.
Remember to be smooth and SAFE. make your hits count and do your best shooting. Dont rush into it planing on going real fast. I cant speak from experience, I havent done any competition... but thats what I've read