Kakuzu in Stamina: 4.5Sasori is way underated. Because he was defeated by chiyo and sakura.
But pple forget that sakura had 3 antidotes, which were all used and chiyo was still poisoned at the end.
Which meant they could have died 3 times without an antidote.
Kakuzu has an advantage of iron skin, and all five chakra natures.
Sasori has the iron sand as defence, which is a very good defence at that.
But since kakuzu has more chakra and needs to be killed 5 times, he takes this with high difficulty.
Sasori in Stamina: 5
Source: Databook
His Iron Sand is all soaked in poison, as well as the weapons in his puppets, Human Puppets, and his puppet body... Poison are everywhere lol, and it's not just normal poison, it's a special one that even he couldn't think of an antidote for it, numbs the body of the victim and kills them in less than 3 days... How cruel!The point is that poison wouldn't react the same because his body doesn't have a normal circulatory system. But, I get what you are saying. The hearts should still be affected. Although, in a fight between these two I think Sasori would rely on Iron Sand and his puppets more than poison.