Well, like I said, fucking Christgau. Lets look at some of his words about all three:
Black Sabbath: The worst of the counterculture (he means counter-counterculture, culture = hippies apparently) on a plastic platter--bullshit necromancy, drug-impaired reaction time, long solos, everything. They claim to oppose war, but if I don't believe in loving my enemies (fucking hippie...)I don't believe in loving my allies either, and I've been worried something like this was going to happen since the first time I saw a numerology column in an underground newspaper.
Led Zeppelin: The best of the wah-wah mannerist groups, so dirty they drool on demand. It's true that all the songs sound alike, but do we hold that against Little Richard? On the other hand, Robert Plant isn't Little Richard...
...If the great blues guitarists can make their instruments cry out like human voices, it's only fitting that Robert Plant should make his voice galvanize like an electric guitar. I've always approved theoretically of the formula that pits the untiring freak intensity of that voice against Jimmy Page's repeated low-register fuzz riffs, and here they really whip it into shape. Plant is overpowering even when Page goes to his acoustic, as he does to great effect on several surprisingly folky (not to mention folk bluesy) cuts. No drum solos, either. Heavy.
Deep Purple: "Smoke on the Water" is about a big fire in Montreux, obviously the most exciting thing to happen to these fellows since the London Symphony Orchestra. No jokes about who's getting burned, though--I approve of their speeding, and Ritchie Blackmore has copped some self-discipline as well as a few suspicious-sounding licks from his buddies in London. Personal to Paul Kantner: Check out "Space Truckin'."