How often have you seen Conti before? Watch him at the under 21 and tell me if you still want him, especially for what atalanta are asking for.
I watched a lot of Atalanta games, they were one of the most fun teams to watch. Every season I try to watch every Juve game plus most of the games of 2 other teams that are fun for me in Serie A, this season it was Atalanta and Napoli.
Anyway, I would want Conti for sure. He is young and raw but he has a lot of potential and is already very good. The only downside of Conti is that he is not the safest defender, this is mostly because Gasperini had him playing wingback all season. As a wingback he is fantastic (same for Spinazzola). As a fullback he will take work, but no doubt that he has it in him. Give Allegri a season with him, like with Alex Sandro, and we'd have ourselves a top fullback.
In the U21 he only played poorly against Germany. Before he was one of the best players.
Given that he is very expensive, and Spinazzola is ours, I would rather we stick with Spinazzola though.