joecool544, for me the 7mm Mashburn Super offers three things:
(1) significant Panache cool factor (2) optimal ballistic and terminal performance given a set of design criteria, performance parameters, available components, and reloading concerns (3)a possible Holy Grail to my never-ended quest for the "perfect cartridge"
I agree the on-game performance of a 7RM or 7Wby would be indistinguishable, but that is not one of my criteria.