Pre-endgame Paladin and Warrior from a White Mage's view.
I just lost my post... urghn!
Pre-end game dungeons (no I'm a Poor Keep or Primal Hard modes), this has been my observation.
Warrior has synergy with AoE damage dealers. I have less MP after the encounter, but the encounter ends sooner. The encounter becomes trickier if there are single target damage dealers involved as after the initial target, if they stray from the Warrior's target, they may end up pulling enmity and requiring Cure IIs to keep them afloat instead of just Cure + Regen and/or Stoneskin + Regen tactics on the tank. If that happens, my MP is usually shot by the end of the encounter.
Paladin has synergy with crowd control. With the crowd control and the Shield Oath damage mitigation, along with the other mitigation abilities, I tend to have a lot more MP toward the end of the fight. This gives me a lot more breathing room to heal people and if things are looking solid, will Cleric's Stance and start rocking the enemy for a few rounds. This style flies out the window if the party does not use crowd control OR AoE attacks are made, breaking crowd control tactics. Things pick up after level 40 for Paladins, thank the Twelve for Shield Oath.
Both seem just as capable in single target enmity, but must be played differently. I've been playing with a Warrior who uses their self-healing abilities in advance, allowing me to keep up my MP and giving them the opportunity to use the self-healing abilities several times during a fight. Where the Paladin would need to anticipate the move and use his/her defensive abilities to mitigate the damage up front. So to me for single-target tanking it's:
Paladins anticipate the big attack, use defensive ability to take less damage.
Warriors get hit by the big attack, use self-recovery ability to recover from damage.
If neither tank uses these abilities, then I will have less MP during the fight. We still succeed and I think y'all will too. But these have been my observations so far pre-50 instances (aside from Castrum Meridian and Wanderer's Palace) as a conjurer and white mage. Hope that helps some.