I'd go with Kisame. They both seem to have a good amount of strength, with A's trump card being his speed and Kisame's being Samehada (in terms of CQC). Samehada would be extremely useful here since it could likely absorb A's lightning armor straight off him. I don't doubt its capabilities, since it has already been shown to absorb lightning release as well as several tails of Bee's V2 cloak. Really, the only thing going for A would be a quick blitz and it's almost a must for him to be in V2 against Kisame seeing how well he was doing against A's brother. The fact that Samehada can heal its wielder isn't helping the Raikage's chances either. Since this is also indoors, Kisame might be able to flood the place and leave A with the burden of needing oxygen. Even if he busts out, Kisame could just move the water with him (water dome). Suppose the lightning spreads through the water: so what? Samehada should be able to absorb that with ease. As a trump card, there's always his huge chakra absorbing water shark.