I had this question come up in my game today because one of my players uses a power sword and shield combo. Under the description of the Balanced trait, it states that the bonus to parry does not stack with other Balanced weapons that the character might be wielding. It does not state anything about whether it stacks or not with another item with the Defensive bonus. My ruling at the time was that they do not stack because logically, you're only parrying with one item. The player felt like the fighting style would contribute to both traits stacking. This approach does make sense to me but at the same time, there's a big difference in the effects of blocking an attack with the power sword versus blocking with the shield (it is not a power shield obviously) as one item has the chance to destroy the opponents' weapon and the other does not.
I was curious as to other peoples' thoughts on this. Should the two stack together? Reflecting fighting style synergy or should it be one or the other, representing that only one item is actually being used to block the attack?