Hey Tim,
I guess the answer I would give is, if you suck at diaphragms It will not matter on which one you use you will still suck. Sorry had to say it, diaphragms take practice. With practice you will improve and will be able to make the most realistic sounds. As far a Glacier Country Calls go, they are one of the best IMO and yes I have used every manufacture out there for one reason or another. My advice would be no matter the call practice, practice, and practice some more. You will be amazed what that can do for you.
Craig