Ah, I don't need to play Zoso again, I still remember it quite well. Just finished 4. In general I think that their multi-part obsession was still rather immature here, their switches are sometimes rather abrupt and illogical, but it shows the way for the grand future (the next two albums which are still probably the best Sabbath your money can buy, along with Master of Reality, if you're more of a
Black Dog / Wheels of Confusion
It's quite possible that one of the reasons for my low overall opinion on Vol. 4 might be the fact it begins with one of the most boring tracks in the Sabbath discography so far. I know it's popular, but the first three minutes or so are just so very teeth-grindingly static ... then the song picks up some steam and the ending is really, really cool, but you have to wait for five minutes 'til you get to it. So Zep get my vote - overplayed as it might be, the main riff is just awesome and the start-stop structure is still fresh after all these years. Also, much as I might dislike Plant in general, he really fits songs like these (he'd be even better on Achilles Last Stand, though).
Rock and Roll / Tomorrow's Dream
Rock and Roll is a fun throwback-y romp, but TD has this wicked earthy riff that wins in this particular competition. Also, it doesn't overstay it's welcome.
The Battle of Evermore / Changes
I'm not a fan of either, but Changes is at least memorable and really sticks out on the album. I think Ozzy's own "answer to himself", You Won't Change Me, hilarious as it might seem in comparison, is a much, much better song, one of my favourites, actually.
Stairway to Heaven / Supernaut
From what snippets I remember from my childhood, Stairway must have been one of the first classic rock tracks I've ever heard (along with Tull's Aqualung). But it's not just the nostalgia factor - the song is very epic and memorable and despite it's so overplayed, I still get my kicks out of it. There's something magical about the intro, its progress into the heavier parts and the solo. I guess the song mind sound dated now, but that has never been my problem. Supernaut is quite fine (I love the latin mid-section), but still somewhat pedestrian, even compared with other songs in Sabbath discography.
Misty Mountain Hop / Snowblind
This one was really easy - MMH is just mind-dumbingly repetitive rocker (they'd try pretty much the same with Trampled Underfoot, but at least that one had the funky edge which this one doesn't have - also, Plant sounds really obnoxious here), whereas Snowblind might be one of the finest tracks on 4. It's much more complex than it might seem, just like The Fugitive.
Going to California / Cornucopia
Another easy pick. You see, acoustic Zeppelin... is always a gamble. There are some awesome tracks (Gallows Pole, Bron-Yr-Aur), but very often it's just rather somewhat boring and melodiless (Bron-Y-Aur Stomp, the song at hand). I won't deny the song has its charm and I'm okay with it and wouldn't think of skipping it, but its three and half minutes subjectively feel like six. Cornucopia might be an updated take on Into the Void (not necessarily a better one, though), but wins this one quite easily.
When the Levee Breaks / Under the Sun
This one was probably the hardest pick, because both songs are pretty great, but Levee probably has more of an emotional value to me. Those run-ups in UTS are slightly annoying (nothing too bad, though), but it's still one of the best tracks on the album, but that Bonham groove on the former is just killer and the chorus, once the song gets there, is just so cathartic and catchy.