All I'm saying is, if my character's bond is with a family heirloom weapon specifically, I would personally pick a fighting style that maxes out the use of that weapon, not my overall fighting prowess.
Picking the AC choice is actually the powergamer move, since whatever extra damage you deal with the final great weapon fighting style is probably inferior to a +1 bonus to AC. And for Protector, our fighter benefits less and less from it (although it's terrific fun), as we fight multi-attacking enemies in larger groups. A +1 bonus to AC is the powergamer move here, and I agree they probably chose it for expediency and simplicity in the basic pregen, but it's certainly not a fun option. +1 bonus is the most boring thing one can think of, and that's coming from a powergamer. Min-maxing my overall character I would definitely pick either Defensive or Protector, they seem to be the strongest mechanically speaking. What I'm actually advocating here is not the overall min-maxing choice, but a crunch choice that more closely matches the bond as stated on the sheet.