Well I think it might depend on whether the 8 inches is bone-pressed or not bone pressed and whether the 6" is maximal girth, average girth, or mid-shaft girth.
My guess is that a true NBPEL of 8" or more is less common than a maximal girth of 6" but an average or mid-shaft girth of 6" may be less common than a BPEL of 8" or more.