As much as i lyk itachi i think i wud pass. although he might b able to win.
1. nagato's weaknes is genjutsu, but he would not fall for itachi's illusion, bcoz rinn is a more ocular power than ms, evry1 knws a normal sharingan cant beat ms. nagato can fall 4 an illusn dats nt by eye, lyk ma & pa's noise genjutsu.
2. nagato can repel totsuka blade wit shinra tensei.
3. nagato can counter ameratesu by absorbing it or by regenerating himself resurectn path.
4 if itachi cant destroy chibaku tensei b4 forming, he and his susano wil b crushed, bcoz only d kyubi survivd it so far.
5. i dnt tink yata miror or d susano can withstand shinra tensei e.g when pain sweep out konoha.
6. if nagato touches once he is gone, soul path.
7. gedo statue
now onto itachi
1. itachi is a genius, if nagato can backup his 5secs interval he is doomed.
2. itachi most upperhand is intelligent fast thinker, his most vital weapon. nagato nt rily bad.
3. itachi's last card IZANAGI, tobi's izanagi last 4 lyk 5 or 10 mins i dnt knw.itachis own might b diff.
this are my advan & disadv. but still d rinnegan is underestimated, kishi hasnt shown its ful details.
this has nothin 2 do wit manga. its a 1 one 1.
itachi has a long shot, but i go wit nagato