I was pretty young during this era, and kind of went back and discovered them both at the same time time. As a body of work, I think that maybe Bark has slightly stronger song writing and composition. That said, I do no like the production on Bark, at all. I tend to listen to records "as a guitar player" and I feel like JEL's playing and tone was superior on Ultimate. And, I feel like Ultimate Sin is one of the heaviest riffs ever associated with pre-Zakk era Ozzy. All things considered, Ultimate Sin takes it by a tight margin for me.