I have to go with Sid by a mile.
First of all Batista may look big, but Sid is a few frames bigger easily. He is the way bigger, way stronger guy, and he is fucking nuts. I don't think Batista would be able to do much to him, he can hardly Batista Bomb Undertaker, and Sid is at least as big as taker, maybe bigger. For the arguments about Batista being faster, that's basically horse shit because HBK was also way faster but that didn't stop slow old Sid from kicking his ass now did it ? Or Bret Hart for that matter. He's just too big, to crazy, and too strong. Batista is a little guy with a lot of packed on muscle, Sid is a fucking giant with a lot of packed on muscle. Sid could easily Power Bomb Batista, Choke Slam him, or anything else he wanted to do. Batista does have a stacked resume but take a look at the names on Sid's and his measures up just as well, he just doesn't have the title reigns Batista does, but that makes sense too, Sid wasn't as marketable guy as Batista, and that right there is the tell all in Batista's success. If he wasn't so marketable with the look he has, he has nothing else special enough about him to make him worth having or keeping. Sid is a spectacle as is, is probably the better wrestler, and has the superior attributes. I don't see how Batista has a prayer.