Does warriors in KMS prefer to max iron body or power strike?
Well, I would say iron body and power strike are not comparable. Power strike is something that every, err most, 99%, warriors master and use instead of normal attack. They do use it as a basic attack skill even after 3rd job advancement. HP Max and Power strike are the ones almost of all KMS users mastered. Iron body will be less important by the time your level is high.