I would take Fed’s 2017 season over Sinner’s 2024 mainly because Fed’s is so good relative to the age he was when he achieved it, and the strength of the field when he achieved it.
Fed’s biggest 2017 wins also came by vanquishing Nadal several times in big events. I’m a Rafa fan, and seeing how Fed was able to do that was amazingly impressive. In Sinner’s case, he didn’t really achieve the same thing. He was amazing against the field, but the power struggle with Carlitos Alcaraz arguably ended up in Alcaraz’s favour, so there were question marks there for me.
As a Sinner fanboy, the matchup with Alcaraz was probably the biggest surprise to me all year. I thought Sinner might have unlocked a bit of gap between himself and Alcaraz in the matchup but it didn’t turn out that way.