In all fairness no version of FFIV has said explicitly what equipping That Weapon or That Armor will do for Those Stats. (Maybe FFIV DS did, I can't quite recall) so from a basic players standpoint it makes a good deal of sense to go with what increases Attack and Defense the most.
Or does he still have stuff like the Blood Sword, Paladin equipment, etc? Also if I may ask, what are you testing?