One thing to keep in mind is that high pitch kills more geese hands down. Having said that, I personally don't like the SR-1. Call me crazy, I just don't like the way it sounds. I do however, like the Littleman but have only tried it out once. A polycarb supermag from Grounds would be a more inexpensive option, and it sounds great. Scott Threinen can attest to that.
My personal choice is the Michigander from Lewis Custom Calls. It is easy to blow and slightly higher pitched. It also has a constricted, straight bore mouth piece which makes the call more responsive in my oppinion. Plus you can get one for $75.