Haku is not really a viable choice , his only ace is his barrier which is a questionable advantage. Ao gives you two clones and shields which is nice but his real ace is his mystery. Though as a downside it seems Ao has a low chance of causing Low float which hurts your combos. Kisame is only good if you're going for control since his mystery drains charka but you need to boost initiative if that's your goal since Kisame has to go first if you want his mystery to be of any use. Kabuto is good for heals and the ability to flood the field with clones , always nice to have a punching bag in front of you after all.