As a point of reference, a first kill t12 recently had Warrior at ~180 DPS and PLD at ~130 DPS. Same ilvl weapon. Warrior wearing +39 Str from jewelry, none on PLD. That's mostly all tank stances, but switching evenly between WAR & PLD MT. Pure OT scenario would be a bit different, but if you can OT 100% of a fight you really should just have another DPS instead of OT.

Fairly certain WAR will always be the preferred OT. Mostly for reasons other posters already mentioned above, but I'll add one more: PLD requires a GCD to switch between Sword and Shield Oaths, while WAR does not require it for Defiance.