I'm the perfect age to be a fan of both, but I never really liked either. I respected Zepplin a lot and didn't really find any redeeming qualities in Sabbath, so I guess I'd have to vote Zepplin, but it's kind of like a lot of elections where you vote for the lesser of two evils. God knows I heard plenty of both - you couldn't go a to keg party in the mid-70s without being run over by both of those bands and I, uh, went to a few keg parties around then. I was always a Stones, Dead, Clapton, Hendrix, Trower guy (and then by '76 or 77 was going back to the source material and getting into Robert Johnson, Muddy, Wolf, etc), and then later Springsteen, Petty, Dire Straits. But I never liked metal at all and I guess Zepplin and Sabbath kind of invented the genre even if they didn't exactly play it - they sure as hell led up to it (pun intended). I shoulda liked Zepplin a lot - I was into the blues from a really early age, but I just never liked how over the top they were with it, either in terms of Page's playing, Plant's singing, or Bonham's pounding away. I really came to like Plant as a solo artist though, particularly the older version.