I can't speak for anyone else, but other than Diary, I very much prefer Ozzy with Sabbath, and at this point I can't imagine a Sabbath song from that era without his vocals. I'm a big "cover" fan, myself - I love love love Beatles covers for some reason - but I just don't find that most bands can really do the Ozzy-era Sabbath justice. Yeah they were "heavy" but that wasn't all of Sabbath's charm, and Ozzy's trebly vocals were the PERFECT complement to the musical sludge.