Nylon holsters do not have any stiffness to them and usually rely on a Velcro strap for retention. My feeling is that a good quality leather holster will hold the gun securely, yet still allow a smooth draw without any snaps, straps or screw tensioners.
After carrying for 35 + years I have finally found what I think is the perfect holster. The Kramer Horsehide Belt Scabbard. It is of the highest quality, thin, light weight, has positive retention with out the use of retention devises, protects the trigger and hammer from unwanted contact, and just plain works! It is also very comfortable to wear all day, and it is not butt ugly like the Nylon ones. I also use this holster in conjunction with his Horsehide belt and ammo pouch. His prices are not cheap, but my feeling is that it was well worth the money.
I personally do not like Nylon ANYTHING. Like others have stated, it has no character, no real shape that is permanent, and other than being light weight offers no advantage to me.
Well, you asked...................
Chief38