Ehh, for me this battle really just comes down to Gai versus Kisame (with Samehada); As Tsunade is not a factor for Kisame and the same can be said about Hiruzen for Gai.
I'd probably lean more towards team two, though. If he manages to create a lake sized jutsu, like he almost always does, Tsunade will be at his mercy as will Gai. Gai has shown to be able to take care of himself when in the water via his gates. Though, I don't think he will be able to cover himself and Tsunade when both sharks and Kisame comes around to absorb her chakra.
And like I said, Hiruzen is a non-factor here. He could really only provide covering fire for Kisame if Gai or Tsunade get too close for comfort or manage to wrestle Samehada from Kisame. But again; With Samehada I'd say Kisame and Hiruzen win this high diff.
I don't see Tsunade lasting in the Water Dome and I don't see Gai in his gated form catching up to Kisame in the water dome either.