Since the topic is about which materia is best for WAR/MRD, I'm gonna step in here and say you'd never want touch of serenity on your gear. If it's on some gear with other awesome stats already such as the Flames Sergeant's Tabard where you can make up for it with jewelry, thats one thing. But you should NEVER add touch of serenity materia on your WAR/MRD gear.