Well, their ontological, epistemological, and ethical statuses, for three. Specifically, how it's possible to want X and simultaneously want to not want X (while remaining more or less sane/rational). Whether metawants have any special status when making utilitarian ethical calculations. That sort of thing. Even the history of thought on the subject (e.g. Buddhism, where the stated (and only?) metawant is to eliminate all first-order wants).