You dont trade Sid unless he asks to leave. He has given so much to that organization, he deserves whatever he wants. Skill wise, in a nutshell, I'd still take Crosby. I'm not convinced Kuch can do what he does with minimal talent around him.
Obv Sid has had talent around him, but he makes no namers look great. Kuch played most of last season with either Stamkos or Point on the ice to work with. Sid has done it with Guentzel, Hornqvist, Sheary, Rust, and Kunitz to name a few over the past 4 seasons.