I've got both... and let me tell you....
PLD has more hate potential....

You can hate on that if you like... But it's true....
If someone wants to sit down and do math... thats fine... lets do it

Warrior is the preferred tank because the HP is just... incredible....
That is the ONLY reason....

the biggest and more incredible enmity grabber IN THE GAME......
EVER AND OF ALL TIME IS:
....
........
..........
AOE RAMPART
Couple that with War drum and your Warrior has to do WAY MORE DAMAGE than PLD to have more hate... more damage than what is possible....

Warrior is the tank because Bosses can hit the tank for 3k damage and PLD's HP just isn't ready for that kind of action
But hate for hate... PLD wins... ALL DAY...

Being physically invincible 1/3 of the time (Divine Veil - 20 seconds, 60 second recast) helps a little... but still not safe enough to say I'd go PLD over WAR in a battle

Also... Collusion is just so much more useful than Cover (Not that cover isn't useful)
It's just easier to know when to use collusion. "BLM, you're about to cast Firaga??? ok, collusioning you now"
With cover.... Its like "If I actually loose hate... I'll cover you"