the reason why nagato was able to do those things in a weakend state wasn't because of the rinnegan, but because he has very powerful chakra from being a uzimaki. the rinnegan provieded the power, but being able to use it when he was weak was all from his chakra.Rinnegan is more powerful look what nagato was able to achieve with pain in his weak state image if he wasnt ill or weak.
Don't know if its more powerful than the rinnegan, but the stages point is valid. Although it could just be because we've only seen one person use the rinnegan, whereas several have used the sharingan. 3 tomoe is no match for the rinnegan but when you talk about MS/EMS, possibly.It comes from Jubi's 9-tomoe Sharingan. I hear some people saying it's a watered down Rinnegan, yet it's more powerful than the Rinnegan and has more stages.