As Yelp has already said...practice is the key. The advantage of a mouth call is lack of movement on your part. In close quarters, that can make or break you.
Also, sometimes some unavailable to get locally, easy to get online, diaphram from a Georgia maker as an example, can sound different that everyone else in the woods with you, with their Primos that, Knight and Hale this....you get my drift. Different can be good.
Don't be afraid of a friction call...box, slate, whatever. Again practice makes perfect. You style of calling can also spell success or failure. Personally I like the boring soft, every 12-15 minutes, pretend I'm a hen type calling which can put you to sleep, rather than I'm going to win this calling contest vocalization.....and all levels in between. I figure the first hour or two is the convincing stage.....like in convincing any turkey within hearing distance I'm the real deal. After that game on....make take awhile, but it always generally pays off.
Not that I don't use other methods depending on bird and situation. Turkey hunting is all about situations and learning. Once you have been there and done that your success rate goes up, as you generally don't repeat the same mistakes.
Good luck..........