Tough one, since I like them both, but only in specific dishes. Depending on the dish, I think of turkey as being too gamey tasting and the meat too fibrous when compared to chicken. For example, I wouldn't want to make a traditional chicken marsala with turkey cutlets - I don't think the turkey flavor would go well with the wine and the meat wouldn't be as tender as a chicken breast. However a large turkey breast roasts up nicely in the oven, and is fantastic served with gravy and stuffing. Generally speaking I kind of treat the large turkey breast much like I would a pork or a beef roast, only that the cook much faster. I'm not particularly crazy about turkey thighs or legs either - since they have such a strong taste, but I can tolerate them in a lot of gravy or shredded into a strong bbq sauce.
I do however like ground turkey over ground chicken in most cases. Ground chicken is often far too sticky, and becomes too dense when trying to form it into a patty to grill or fry. Turkey will maintain some of it's texture, more like a ground beef patty, when compared to chicken. I also really like the flavor of turkey in meatballs and sausages.