In early end-game (read: Heroics and 10 mans) Warriors will have certain advantages over Paladins. Namely, they get a higher base health (Especially you filthy Taurens!), higher mitigation, and more "Oh sh*t!" buttons.
Warriors have multiple spell casting interrupts, all on relatively short cooldowns. Warriors can hold tremendous threat in an one-on-one encounter. If things go to hell, they can increase their lifepool and become nigh invincible. (Last Stand/Shield Wall). They can also stance-dance out of fears.
Their shield block gives them an immense amount of shield block %, allowing them to become uncrushable with the barest amounts of gear. Because of rage mechanics, as long as they have health, they can keep on fighting. (Assuming the mobs hit them hard enough) Warrior's threat scales with shield block, effectively allowing them to hold more threat as their mitigation improves.
Paladins have much different strengths/weaknesses. They are inherently squishy, their lifepool not comparing to that of a warrior's. (At first) Their shield block is only a 30% increase (Math not so EZ), which means much more gear is required to become uncrushable. However, their shield block lasts for many more charges than a Warrior's. Once a certain threshold is reached, a Pally tank will *never* be crushed. (Barring stuns and the like) Their threat scales with spell damage, arguably faster than a Warrior's.
Mana allows the Pally to front-load threat on a mob, and their "blue rage bar" mechanics allows them to keep on going assuming they get heals, but if they go OOM, agro generation pretty much stops until they get enough mana back from heals.
Their one-on-one threat generation is decent, but because of the class mechanics, Pallies can hold an infinite amount of mobs, heals permitting. As for "Oh sh*t!" buttons, Pallies only have 2. One will heal them to full, possibly avoiding a wipe, at the cost of lowering their agro generation for a while. (IE: They OOM when using it) The other is terribad for tanking, BUT has some uses (Namely if everyone else is dead, it buys 12 seconds of lawlprot DPS).
As for spell interrupts, Pallies fail horribly. Alliance Pallies have 1 interrupt, one which has a 1 minute cooldown. Horde Pallies have 2, on a 2 minute and 1 minute cooldown.
The Paladin pulling method is also, sometimes, superior to the Warrior's. With their shield, the Pally can instantly put a large amount of threat on up to 3 targets. Since post 2.4, the shield does not break CC, allowing the pally to throw the shield with impunity.
Tanking wise, Warriors need to press more buttons than Pallies. I press 3 buttons to tank. (4 if it's a Demon/Undead) My friend needs to keep up a certain rotation in order to tank on a Warrior.
tl;dr: Warriors are easier to gear up than Pallies and are overall easier and more forgiving of errors. Properly geared, skilled Pallies are monsters.
Irregardless, both are situational, and there are times when a Pally tank will shine, and vica versa.
Edit: Zomg, wall of text!
Edited, Apr 25th 2008 11:23am by Zeromatter
Edited, Apr 25th 2008 11:57am by Zeromatter