The biggest change to me that will make PLD so much better is if they put the Oaths to where it does not trigger GCDs.

Since PLDs can now block magic in SB, you have to pick based on the mechanics and your play style.

WAR: Has more dps due to a better dps stance and attacks

PLD: Better defense (for party) as they are more align as being actual tanks. Can make for a little hard to maximize as some abilities require positioning such as the new wing move and the wall they can put up from time to time

DRK: Requires more control over resources, but can be a decent balance between dps and def. If done right with a 1 attack buff, can put out some nice damage and debuff

The biggest problem is that with Stormblood, we do not know all the changes. It could be that with the plan to close the gap between casual and hardcore players, that everything that is in HW will become invalid and have to learn how each tank works with the raid and party composition.