After reading this I made "burgers" with ground chicken thigh. (Didn't have turkey thighs handy.) I have the feeling chicken thighs have plenty of fat, so less likely to dry out than turkey, but it occurred to me: what are the pros and cons to removing skin before grinding poultry meat? Especially if the complaint of turkey "burgers" is that they are too dry and lack flavor, wouldn't the skin help with that?
I think you hit the nail on the head when you mentioned fat. Leaving the skin will give your ground poultry a higher percentage of fat content, resulting a more tender and moist "burger".