If pressed to single out only one favorite, Sabotage would be my top Sabbath pick. It's more polished than their earlier work, sure, but it's also one of the angriest records any of those guys have ever been a part of. It's also the best Ozzy has ever sounded.
I actually have the original vinyl record, which came out 40 years ago today.
And, full disclosure, there's very little Sabbath I don't like. And I'm including the post-Ozzy, and even post-Dio years in there.