If it is strictly from the lore stand point i would say the SCH. Because we finally find out the origins of the Tomberry plague and the name of the 3rd misterious black mage civilisation.

I was so dissapointed with the PLD story. I had to re watch all 50 - 60 couple times to finaly understand it. At least, we fight the PLD leader, but that only lol.
Still despite I have being a PLD for a long time, I still dont know what is the PLD's inner strenght. Wars have inner beast, DRK have the darkness. What do we have PLDs ?