Good answer.Bret said:A double reed call offers a second reed that acts like a baffle that makes it harder or impossible to squeel out over the top. The baffle does limit range of tone and sometimes volume, but doubles are often very ducky sounding. Doubles often load up collecting to much moisture between the reeds locking them up. A single reed offers full range of tone but is sometimes harder to control. A good single in the right hands is a beautiful instrument. They are less likely to lock up however many of them will. I blow singles most of the time I like them because of there range and simplicity.
I look at it like this if you want to spend some time learning how to properly operate a single reed call then you should get a single. If you want to spend less time get a double either will kill ducks just fine.
there are many good calls out there. Foils makes a nice call, but there are many other nice calls check out a bunch before you buy. blow as many brands as you can then pick the one that runs best for you. I like to hunt with a Rowdy DOA double trouble tuned as a single (They wont break the bank either). I also like Giden calls and Swamp thing Mallard calls for hunting. Pick what works for you.
I hope this helps some.