They could be called the first testament and 2nd testament when it comes to looking after ourselves.
What I find really important is they compliment each other. Mark covers the diet, while McGuff and Little cover the heavy lifting. Their concepts of hunter/gatherer foods and the importance of heavy lifting are the same. Mark covers the diet and BBS covers the lifting. It blew me away when McGuff mentioned on his website he takes Mark's supplements.
They have some slight differences, but that is good. It means we continue to review and research what to do what is best for our own personal achievement.