I believe as a turkey hunter it is important for you to not just rely on one call. Having a good understanding of how to use all calls will help. I can't tell you the number of times I have been in the woods when one turkey wanted to hear a box call, another wanted to hear a slate call, and another wanted to hear the diaphram call, or even another call, be it a wing bone or another friction call.
You certainly don't need to be an expert caller either. Just enough to let the gobbler know you're in the area.
And remember do not overcall, chances are you will spook him or not even hear him coming in if you only concentrate on your calling.
Dean, I believe you asked our opinion of the Best Turkey call, here's mine. IMHO the best call is either a wing bone or a tube call. Why? Because they are difficult to learn and for that reason, very few hunters use them. Hitting that ol Gobbler with something he's not already conditioned to steer clear of is a recipe for success.