I've found diaphragm calls to be very easy with a little practice. I stick a couple in the truck a week or so before season starts and practice a little driving to and from work. I've never won any contests but I've killed lots of turkeys.
I've tried all the others but they create too much movement and/or necessitate a last-minute switch from call to gun.
I can't recommend a brand since everybody's mouth is different but I've used Quaker-Boy and Primos and they work good for me. I also prefer double or triple reed styles because they sound like a raspy old hen IMHO.
I also don't do locator calls anymore. I've just never seen them work with any regularity. A really aggressive cackle like two hens fighting usually gets 'em to gobble if anything will.