User blog comment:SlashZero/Spring 2016 E-7 Hard Pre-final & Boss Farming Composition/@comment-24894280-20160525082405/@comment-861160-20160526023214

Well, if you follow my advice Bisko will be set as flagship. Flagship is probabilistically the least likely to hit the boss in night battle, therefore the torpedo stat on Bismarck isn't wasted if she hits Senkan Seiki or something. Also that torpedo can do non-negligable scratch damage during the day too. I don't see a great advantage for Bismarck Drei over other FBB as a 5th-6th slot, but as flagship it makes sense.