Ah, so you finally come up with it? Cool.
I always saw Kakuzu as the superior combattant here for these reasons:
- He has 5elements, while Kisame only has one element. While his suiton is greatly overwhelming, since it's a suiton base it can't kill Kakuzu especially when he is protected by the doton domu(doton>suiton)
- Kisame is alone and he will be facing 5opponents(Kakuzu and his masks) and Kisame doesn't have enough of speed feats. In the contrary, he usually takes damages(whether he wants it or not), so facing 5opponents, i really doubt he can handle all that. Even Kakashi with the sharingan had difficulties to keep up, and we all know how fast he is, we all know the advantage of precognition that Sharingan gives, so there is no way that Kisame could keep up
- You may say that Samehada could absorb attacks which is true, but until when? And could Samehada really absorbs attacks coming from 5directions? To absorb chakra, kisame usually puts Samehada infront of him to protect himself and absorb it, so if Kakuzu attacks from 5different directions, how does he protect himself with Samehada, and avoid damage? And that is when i forget the fact that manga has already shown that Samehada doesn't like fire, so the overwhelming katon jutsu Kakuzu has shown would cause great troubles to Samehada
- So if they fight outside water, Kisame has absolute no chance and i didn't even mentioned the fact that Kakuzu has 5hearts, so Kisame has to kill him 5times. Now Kisame will most likely use his water dome, but could he really use it in same extent than against Killer-Bee? I doubt simply because remember that he absorbed Hachibis chakra before that moment and it's the reason why it was that big. But still, even if he manages to do that, Kakuzu only has to do his best to get out of it, because inside it, Kisame will be at his advantage.
Kakuzu having 5bodies is greatly advantaging him here in this situation. With some of his bodies, he can create diversions to feint Kisame, and find his way through. With his fuuton attack for example, it has enough power to blow away a great part of Kisames waterdome. At that moment, he has opportunities to go outside of it
Fighting outside the dome and Kisame is screwed like i've said. Even if we imagine a scenario where he loses one of his heart, he can play death and catch Kisame by surprise. I'm not sure if Kisame knows Kakuzus secret, so he could be surprised
So overall yes i agree, Kakuzu is stronger than Kisame
