I don't know if effectivness can be acurately determined b/c the sound of a call is by personal preference. If you prefer glass over another surface then that's the call you'll use the most "ol faithful", you'll have more confidence with the call & you'll practice with it more. Same goes for the other surfaces as well. I think IMO it would be totally impossible to find someone who doesn't have a preference with one or the other to use all on a constant basis in a study. They all work well on getting the job done, they fool Gobblers every year. My .02