what makes SK > War and Pally?
Lots to unpack. I would start by saying any of the three are completely capable of anchoring a routine group in current content.
Both of the knight classes are better at holding the mobs attention, but the warrior can do it just fine too. The Warrior has higher hp and ac, given equivalent gear, and you can push yourself a little harder with a warrior. Not much but not zero. None of the three are going to get a great DPS, but the SK probably does the most unless you're fighting undead then the paladin can give bonkers deeps.
There is rarely any need for exotic pulling, just run up and bring the crowd back with you, but if there is occasion to split a camp then the sk is best at it, a pal can do it some with harmony but don't count on it much. a shadow knight can get snap aggro easier on a group because they have 'joo Pay attention to me now' ability that the other tanks lack. So ae tanking is a bit simpler on the sk, at least if you need snap aggro. A pal generates substantial threat on a group by healing. I personally have never found their area threat lacking, although they don't have the same tools to snap ae aggro as a sk.
A warrior has very little healing abilities, an SK is good at keeping themselves topped off, a paladin can heal the whole group.
Warriors are usually fugly ogres or trolls, SKS can be Some of the cute races, only Paladins can be a high elf though and they're my favorite. So QED.
TL;DR They aren't, play what you want
