Warriors have much easier time with AoE packs. Assuming no support in the team, if the paladin takes any additional damage other than the boss basic attack, it usually goes right through the barriers - which makes certain fights rather painful (for example Turtle Island 3rd boss, you can get surprised by the Thunder phase if you haven't been there yet).
Paladin does have really nice party support, but it's rather situational as well. However large shield thingy and the heal are really long cooldown and your only real party-wide shielding skill is from the Defensive Screen.
Defensive Screen requires you to have an active barrier, so it can be pretty awkward to use at times (like in Plague City last boss, you actually have to walk into the green crap on the ground to have a party-wide damage mitigation up).
In the end warriors can achieve about the same effect with the Turtle shield rubies and so can Scouts with the Joker effect - there's not really a huge difference between any of them for PvE from what I've seen.
Out of the 3 tank classes here are the only significant differences I've found:
- Warrior seems to be the only one which is actually useful as a tank in PvP
- Scout is rather entertaining to tank with
If you are trying to decide a class based on that, you should probably just pick it with PvP or your group in mind.