When merging release groups, on the preview page you are shown for each release their titles, their artist credits, types, earliest release year, ratings (least useful of those) and release count in each group. Yet the release edit itself shows only the first two (title and credits). I find that at least release group types should be also displayed on the edit. For example, it is not uncommon for an album and a single by the same artist share identical names. For other information (besides rating) I see less use in this case, but it likely wouldn't hurt either.