Nagato can defeat Sasuke's Susanoo, and Sasuke for that matter.
Animal path, Deva path, Naraka path, Pretta path are the main factors in this battle. Multiple summonings overwhelming Susanoo, the arrows won't work on the multi-headed dog that multiples when it's hit. The others can die, but that dog is practically invincible and Susanoo's attacks won't work on it. Repell and attract, repell Susanoo's attacks, draw in Sasuke. Naraka path only use is restoring dead paths. Pretta, Susanoo's attacks are chakra based therefore can be absorbed by the Pretta path also nullifying it's affects. I forgot about the Deva path's Chibaku Tensai, which can seal away Suasnoo. That is my belief of why Sasuke's Susanoo doesn't work against Nagato.