Prime Madara had Eternal Mangekyo. Not Rinnegan.Prime Nagato had Madara's EYES!! Nagato is on borrowed eyes. It's not like he had his own sharingan and went through the motions. No he had someone's eyes. He can't beat Madara. Madara knows all the Rinnegan's secret because he unlocked it and I'm 100% sure that he tested out all the jutsus so he could get a basic understanding. Madara is a machine bred for war. Hashirama is a machine bred for war. There is no one out there that can solo either of them.
Madara unlocked Rinnegan when he was an Old Man.
That was when he taught Obito everything he knew before he died.
If we're talking 'bout Prime, Nagato wins this.
Prime Nagato had Rinnegan. Prime Madara only had Eternal Mangekyo.
Rinnegan > Eternal Mangekyo > Mangekyo > Sharingan > Byakugan (ROFL!)
I'm not saying Rinnegan Nagato > Current Madara on the battlefield. Madara would eventually overpower Nagato if that actually happened.