Two years ago I wrote, that prefer Purple over Led Zep, and now I've wished to explain, why. I just think, that in their best years (I mean 70's) Purple were better as musicians separately.
Ritchie was more technical skilled guitarist, than Jimmy, Gillan was much more better live (and studio) singer, than Robert, Paice was more stable and versatile drummer, than Bonzo (with all my respect to Mighty John), and, of course, Lord always was much more better keyboardist, than Jones (although, for the sake of justice, keyboards wasn't John Paul's main instrument).
IMO, LZ had only three undoubtedly advantages: John Paul Jones always was much better bass-player, than Roger Glover, LZ were much more skilled and professional arrangers, than DP, and sure, they're had incommensurably better management, than Purple.
I'm sure, if DP, Uriah Heep, UFO and Nazareth had such a manager, like Peter Grant - their popularity (especially in USA) could be not less (and, maybe, bigger), than Zeppelin's.
So, final score (for me) - Purple a bit better, than Zeppelin.