Big difference between duck and turkey. First off turkey has alot more meat on it (bigger breast and legs etc, and thats where alot of the meat is located). I like the neck also and turkey has way bigger neck.
Duck is also all dark meat. Duck also has a fatty layer under the skin, some people like though because it makes it really greasy and fatty for flavor, so where a turkey the skin bakes crispy, duck it doesnt because it thicker and fatter. It really just depends what you like or how many plan on eating it.