I use/have used many different types, and I've found that some will be more effective than others on any given night. For the last 10 years or so I've stuck to what for me work best. They are: Wam, Foxcall, and my hand.
I think that more important than the make or model of the call, is making a realistic sound, so when buying a call, my advice would be to get one that you think sounds right, and get in plenty of practice.
Hope this helps,
Kenny