This is a good argument. However... how and under what circumstances?A powerful user can control Kuybi. Kuybi is stronger than Nagato i hear no argument for this so i guess it is settled. And do not tell me the shit that it is sealed inside Naruto because then i wil say that Nagato is dead. Also do not say tell me that Nagato used only one body because i wil say that it was only eight tails and half the power because of yin and yang. And also the user that controls the kuybi will fight alonside.
Firstly you need Kyyubi to appear and only then you can control it. Kyyubi is a natural disaster... in order to gain control over Kyybi, you need to find it and get it. You need it to appear. And kyybi appears very rare so....
And also who said that you can fight alongside, while maintaining the control over Kyybi ? - speculation?
Also you have brought Nagato into this discussion but Nagato is Nagato and Rinnegan is Rinnegan. The powers of Rinnegan depend on the amount of chakra the user has. Sage of six paths could create a moon and NO WAY could Kyyubi withstand that pressure. 8 tailed Kyyubi struggled to get out of 50x50m Chibaku tensei, dont tell me it could escape from 8000kmx8000km ??
Really, you sound a little bit biased towards the sharingan. Even saying something as arbitrary as "A bse sharingan is stronger than rinnegan" in the other thread.
Just for youtr better understanding of my points:
1) Kyyubi is a natural disaster and appears very rare. Therefore Sharingan has to wait for it to appear.
2) Pein doesnt represent the full power of Rinnegan. All the jutsus were just as strong as their users. Sage of six paths could create a moon. Moon > Kyybi.