Few clarifications between paladin/warrior

[Snorgrind]

Just to be clear, the HP makes no difference. PLD and WAR benefit equally from Stoneskin and Adloquium. While WAR will receive a stronger shield by number, PLD's shield will wear off slower because of mitigation. (Adloquium is actually better on PLD because they receive minimally larger heals when mitigation is counted in, but that's splitting hairs.)

exactly, ppl need to get it out of their heads that stoneskin and adlo is better on war, everything is better on PLD by 5% (shield oath vs defiance)

[Traek]

exactly, ppl need to get it out of their heads that stoneskin and adlo is better on war, everything is better on PLD by 5% (shield oath vs defiance)

Stone Skin is equal on WAR and PLD (you might have meant this), but Adlo is definitely splitting hairs better on PLD.

Do the two stances offer about the same benefit, or is shield oath just much better? A warrior not having the 20% mitigation would mean it would take more mana to heal him, although he has the 20% cure increase (and more hp), so does it end up evening out?

It has been answered many times, and I advise perusing these tank forums, which many of your questions will be answered. In the end, both tanks if played right are very near equivalent since 2.1. Play which one you like, and/or what is best for the fight at hand. Shield Oath > Defiance *technically* because of the 5% difference in healing received (25% native to Shield Oath, 20% Defiance), while -20%DR = +25% HP. Warrior should make up the tiny difference in IB/BloodBath. Again it is splitting hairs.

Also don't underestimate Marauder's skills such as Bloodbath, Fracture and Vengeance.
Together they heal you thousands of HP while active and Vengeance also causes damage to enemies attacking you.

Eh.. Bloodbath and Fracture are hardly something to consider in the equation. If a Warrior is pulling 180 DPS (pretty generous for the average and vast majority of 'meh' Warriors), over the 30 seconds (numbers can be further padded with zerk/unchained of course) they'll heal themselves for 1350 over the course of the whole CD. It is basically the equivalent of one Cure from a geared healer over that 30 seconds. Not to mention you can be topped off for many of the hits, which will just be over-curing on yourself, adding to nothing.

Fracture is a TP starve for minimal DPS increase. Use it if you are in a fight you aren't going to bottom out in TP, or disengaging a boss for encounters, but most of the time it is not even in the rotation. Keeping up debuffs is a higher priority anyways.