Its time to put this to rest.
Firstly its a myth saying genjutsu wouldnt work on sasori. True he doesnt have a brain, but if he doesnt have a brain he should be dead. He cannot control his puppets without having a brain. What im trying to saying is that the fact that he doesnt have a brain yet he can control his puppets should tell you that logic doesnt always follow in anime/manga. Therefore we cannot for sure say that genjutsu wouldnt affect him.
Now if genjutsu affects him, then itachi would no doubt win. If it doesnt affect him, sasori wins with mid difficulty.
Now itachi should get past sasori's scorpion form with ease. It isnt fast enough to evade amaterasu, but also its wood. fire> wood.
Sasori would then use the 3rd kazekage. This will cause itachi problems but again i can see him getting past the 3rd kazekage. By the time itachi has gone past the scropion form and the 3rd kazekage, he wouldve used about half his chakra. He now has to face 100+ puppets.
In such a case he cannot evade all of them, not even itachi. He would have to rely on susano for extra protection. Now if his chakra is has already been halved and is using susano, how many of those 100+ puppets can he take out before he eventually dies of 0 chakra, or even poison due to sasori.
What im trying to say is that itachi we all would agree is stronger than sasori, but there is something called bad match ups. Sasori has way to many puppets for itachi to take out before his chakra runs out.
Also alot of people are underrating sasori greatly. If you read about him, he is also a child prodigy. He deserves his 5/5 stat for intelligence
