Windwalker monk has a higher skillcap (requires more skill).
I currently still play a windwalker monk.
And whenever I go back to the other classes, they all seem so easy to play compared to my windwalker monk. For example, I can kill other players much easily on my warrior than my windwalker monk. It takes me a lot longer to kill a player on my windwalker monk in the arena. But on my warrior, it is pretty much GG. I just pop my recklessness, bladestorm and it's GG, lol. But on my windwalker monk, I have to sort of set it up. Windwalker monks can't just pop a cooldown and all of a sudden do tons of burst damage. They have to BUILD UP their burst, build up their tigereye brew stacks.
Same with ret paladins. They just pop their Avenging Wrath (wings), Holy Avenger (if talented), and it's GG lol. They have incredible burst as well.
But windwalker monk. It is a lot harder for me to kill a player in the arena/bgs because they require a little more skill than all the other regular classes that have been in the game since launch (vanilla wow).
Because WW monks have to build up their burst, Warriors and such pop CDs and one shot people that is why Monks are more skilled than these classes and managing your energy is difficult if you are new to this class. I only play WW in BGs/arena I do not really like to raid with WW monk as there are better DPS classes to fill the spots so I tend to change to MW or even BM as I enjoy every spec of the Monk.