Rokushiki is pretty much "six styles", used first by the members of CP9, Lucci, Kaku, Blueno and Califa. It's essentially six moves which are very skillful, which to accomplish without this would push your body to the max, or just be impossible.
Kami-e: Translates to "paper drawing" and allows you to dodge all attacks, like you were paper.
Soru: Which is like light-speed movement, so it's just moving so fast the naked eye can't see it.
Tekkai: Stiffens the muscles so you can take on a much more powerful attack without budging.
Geppo: Translates to "moon jump" so you can jump in midair.
Ranyaku: Air Slice, so it's like a slice in the air like with a sword, but not.
Shigan: Finger gun. You move your finger so fast into someone it looks like a bullet penetrated them.
But to the question, I'd have to go with Haki. It's muh better to be able to know your opponent's moves before they use them.