I carry all 3 types into the woods with me. All of them have done the trick for me on different occasions. The slate seems to work best for me when using soft clucks, purrs and yelps. The aluminum and glass surfaces are louder and I like to use them when I am calling more aggresively. Also the type of striker you use with each surface changes the tone and volume. My personal favorite is the aluminum surface because I can call soft and loud with it.