While they may indeed be the same 'baccy, McCranie's is specific to a certain crop year which is listed on the tin. Seems I read something that they specifically choose a crop year that they feel best represents a straight red 'ginny.
I've smoked enough of McCranie's Red Ribbon/Red Flake and McC 5100 to declare no appreciable difference, and I smoke 5100 regularly as a result since the bulk is so much more affordable.
I guess if one was looking to know what year the 'baccy came from and were willing to pay a little more, McCranie's certainly offers advantages. The newest iteration of it on offer is 2008, so it's certainly well aged.
FWIW
Cheers,
RR