The moderate rooms are smaller and open to the outside, there is less dining options, the location to the parks or one or 2 parks, full room service I think is only available at the deluxe resorts, fitness center in some.
Besides what has already been mentioned, almost all the deluxes have the option of a table service lunch. And all (?) give multiple options for table service dinners. (Admittedly, at the Beach Club this would require a short walk to the YC if you want something other than Cape May - reopen Ariels!!!.)