nagato became wht he was after yahiko died its like itachi is a bomb but made carefully able to use all its potentials while nagato is a beast created in accident in the age of ten years able to manipulate all the elements and the yin yang chakra and u still say he is weaker than itachi nagato cannot fight while kabuto controlling him because kabuto doesnt know about the powers of rinnengan as well as tobi or nagato
I am going to tell you this again, I don't care how many powers you can tell me. To me, the most important power is to have the intelligence to make the best out of them and have the intelligence to come up with strategies. Intelligences is what makes Itachi and Minato very very powerful ninjas
The last time I have seen Nagato use the elements was when Jiraiya help him learn them. It's not like he did it alone. Nagato didn't know what he had and what he was capable of until Jiraiya told him what little information he knew about his eyes and helped him control the other elements. After J-man left them I have not seen Nagato use his elements other than creating rain and stopping it. A ninja uses their strongest jutsus and what they feel comfortable using. Nagato chooses to use his other jutsus and not his elements because that's his most powerful jutsus and that's what he is good at.
Nagato got hit by amaterasu and Kabuto helped him recover. I don't know what you mean by saying that Nagato would have done any better if Nagato wouldn't have been controlled by him but I don't believe.
First of all, Nagato was in a wheel chair. Every attack he used, it was a great deal of risk for him. He even started to bleed from his nose and mouth. He was weak which is why he chose to get dead bodies to do his work for him. He didn't tell anyone his whereabouts because it was too much risk for him. Jiraiya would have defeated Nagato/Pain if Jiraiya knew about his secret about him hiding in the highest tower to control the bodies.
Second of all, the attacks he perform to gain his complete form, correction, The attacks Kabuto performed to complete Nagato's form was very well done. He took bee's chakra and immediately after took naruto's chakra to complete his form.
It was only because bee and naruto were there that nagato was able to return to his complete form because both naruto's and bee's beasts have immense amount of chakra.
Since you are saying that naruto and bee helped Itachi get Nagato. It goes the same to Nagato's too. Naruto and bee helped Nagato complete his form.
If you exclude naruto and bee from the fight then you get a fully healthy Itachi against a weakened Nagato.
But I am SURE that Itachi would not have asked Naruto and Killer B to help if he was sure that he could destroy the Chikudan Tensei himself!!! He'd do it himself - he's a person who resorts to other people's power only as a last cause. He depends on his own power otherwise 
