I don't know that I agree with that. Given I've never seen Led Zep live, though I did bump into Robert Plant coming out of Heals on Tottenham Ct Road once, but I've watched countless video of them. Yes, the first 5 albums are awesome, Presence being a kind of half and half transition album into their autumn days and not really making the mark. But the live performance wasn't so much about the quality of the sound, or the accuracy of technique, it was about the Thor-like fury of Bonham's arms, the exultant flash of Plant's mane as it caught the spotlight, the dark brooding calm of Jones's bass and keyboards and, of course, the arrogant shivers of Page's electricity.
There's a bit in the 'Song Remains the Same' concert video, where you've just been backstage and Plant's been going on about 'the cosmic energy hits you and you go wah, bam!' and you're immediately assaulted by Page going nuts on his Les Paul before relaxing into 'Since I've Been Loving you'. Anyway, when they get to the solo, you spend a few minutes with the cameraman panning around the members of the audience, mostly settling upon a spaced out brunette, with blue eyeshadow, who's clearly feeling the whole performance on a narcotically enhanced level, until you alight upon a security guard who's just standing there, hands dropped, jaw slack and mouth open in sheer awe at what's happening on stage. That, for me, says more about Led Zep, than anything else. Yes their album work was amazing, but their live performance had an awesome quality to it, and even their live studio stuff, like the BBC sessions, showed this.