Hashirama - Can give insight to how the Uchiha were in the past and can see if the Senju wanted to suppress the Uchiha when they formed Konoha.
Tobirama - Give answers about the whole Konoha police ordeal and if it was based on his suspicions about the Uchiha or not.
Hiruzen - Can give the most information since he was alive when the massacre was orchestrated and had lived the longest so has seen the Uchiha in different generations as well.
Minato - Can talk about the masked man and Sasuke will probably infer that it was Tobi who attacked Konoha and it shows that Tobi (Obito) lied about the Nine tails attack being a random natural occurrence.
All of them have something of worth to tell him. It also ties into to the present. Hashirama if he and the Hokages get to the battlefield, will get to see Madara, Tobirama will see the ramifications of his jutsu, Minato seeing his son etc....
