I kept with the traditional gun on Balthier and bow on Fran. My gun with 'low attack power' and its defense piercing does more damage than any of my other characters except for a Bravery-ed Vaan 5 levels higher. I have Assassin Arrows on Fran, so about 25% of the time she insta-kills. Obviously every weapon has its strong point - poles chain attacks better, for example.