If Nagato starts off complete, I'll be placing my money on Nagato for this fight
Amaterasu and Susano'o arrows with both be absorbed, if he's mobile Totsuka won't be hitting him, and honestly, I don't honestly see a way for the brothers to win, let alone survive Nagato's barrage of Shinra Tensei's (would easily throw their Susano'o) and Chibaku Tensei, since two Magatama's doesn't seem enough to break the core
Human Path + High Powered Bansho Tenin'n once Itachi is re-assembling would be sufficient to seal him