I've leveled both and I personally prefer WAR.

PAL was so difficult to level in the early dungeons for me, I'd stay on top of my rotation, flash, and provoke until kingdom come and I still had problems keeping consistent hate on everything that was thrown at my group...the struggle was real. There are a couple in my fc who main PAL's and they are such awesome tanks and know the class so well. The damage mitigation tools of the PAL easily make up for their lack of a massive tank health pool. I main a SCH and the PAL and SCH work so well together.

WAR is a nice brute force play style that can take the hits AND give them out, with a heavy reliance on class competence to be able to use skill combos to work with a large health pool to be able to mitigate damage. My advice is try both and see what play style you prefer.

That being said, I look forward to the dark knight's play style and how it differs from these two :O