Jeff, I aint taking sides here, cause I don't care, but the differences, no matter how small, are measurable. For most any practical purposes, they will perform similarly. Use what you want, no-one cares, but he isn't wrong.
I know for a fact that a .300 Weatherby has superior ballistics for big game to a 6mm rem., but I can still kill stuff with the 6mm.
I don't have to be "right" to justify using the cartridge of my choice, no matter the reasons.
To argue with a man who has the physics on his side to justify your preference is just silly.

Democracy is not freedom. Democracy is two wolves and a lamb voting on what to eat for lunch. Freedom comes from the recognition of certain rights which may not be taken, not even by a 99% vote.
*Marvin Simkin* L.A. Times (1992)