Sinner is a clear favorite IMO. He's been on absolute fire since the USO loss to Zverev while Medvedev's play has been uneven, there's nobody playing better than Sinner the last 4 months.At the same time, Medvedev is ranked higher, has gotten over the big hurdle already of winning his first slam, and is generally a lot more experienced of a player. I agree that Sinner is probably in better form. Yet, Medvedev is also in very good form. Taking out Hurkacz and then Zverev proved that.
You could really make an argument for either. I don’t think there’s a clear favorite. Everyone was talking about Sinner beating Djokovic of the two semis, and that’s understandable why it’s more than just the quality of the opponent on the other side of the net that he beat. He beat a dominant figure at arguably his best tournament. I think though that this match has no clear favorite, even if some will try to make Sinner into a huge favorite for reasons that I’m not sure are necessarily a positive.
You can never count out Medvedev on hard courts because he plays the type of game that can frustrate anybody but Sinner just seems destined to win this slam. Sinner isn't a huge favorite but he's the favorite for a reason. The one thing in Medvedev's favor is experience, he's done this before while Sinner hasn't plus there's always the chance of a letdown factor after beating Djokovic but Sinner seems laser focused mentally. Should be interesting either way, complete contrast of styles clashing.