Double reeds are typically a little easier to blow, they don't require as much voice to get the ducky, raspy, lower end sounds and for many beginners are a little easier to start making good duck sounds with. Double reeds are usually limited on the high end of the spectrum for contest style hail calls. Single reed calls typically require a little more voice to get the correct sound and for most beginners require a little more practice. Most callers find the single reeds more versatile throughout the whole range of duck sounds. I do not claim this to be facts, only my observations. Every duck call will match every duck caller differently.