John,

I think you bring up an interesting point about genetics.  Even within the Hereford breed there can be large differences in REA (rib eye area), IMF (marbling) and FAT (external fat over ribs).  So in either breed (Hereford or Angus) there can be a wide range of beef quality and characteristics between animals.

That is the benefit of having EPD's and should be of particular interest to freezer beef producers. Here is an interesting explanation of Hereford EPD's. Age at harvest is another variable. Lot's of things to consider but genetics is the start of good beef.

Jim at Dawn