I can't answer your exact question, but I think I can contribute something. I'm a very small custom holster dealer. I'm not trying to do any business here and I don't even rep anyone who makes a flap holster, so I'm totally objective. BTW, I have no experience whatsoever with any flap holsters.
I ordered a "Tom Threeperson's" holster for my custom single action from El Paso about 6 months ago. It was pretty standard with basketweave stamping. The holster arrived exactly when promised, but the retention strap was a bit short. My gun is a custom so I wasn't surprised that it wasn't exact. They were very polite when I called and told me to send it right in, which I did and to my surprise I had it back in two weeks, fixed perfectly. The workmanship is very good, not a bad stitch anywhere, and I would order again. Keep in mind that I'm a holster seller myself and hold the provider to a higher standard. I was satisfied.
Another holster for a revolver that I've been very happy with was one from Mernickle Holsters. Mine is the model recommended by JT, and it doesn't have a flap. They DO offer a flap model however, listed under Field Holsters. No problems of any type here either...Tom