So the main differen in PLD and WAR is that WAR can deal more DPS and can inflict Slash Res down on targets and WAR makes a great OT.

PLD on the other deals less damage but not that much less damage. PLD is more a bulky physical deffence tank thanks to it's STR down, shield, and shelltron.
Not to mention it has some nice party support like divine Veil, stone skin and protect.

BUT bear in mind both tanks can easily clear any current content out there some will have there advantages over the other but nothing too big.
It's balanced really well.

So it all falls down to what you prefer to play.