I've always loved this debate, though I do think it's comparing apples to oranges. My two favorite bands of all time are Led Zeppelin and The Who, in that order and have loved both since I was a young teen. I readily admit that Led Zeppelin is the better band, but it is a lot closer than most Led Zeppelin syncophants admit too. Led Zepplein easily wins over The Who with it's non-live recorded material. Jimmy Page was an amazing producer and every Led Zeppelin album sounds phenomonal, even towards the end of the carrer when Plant's voice wasn't as good and their songs were substandard compared the their brilliant first four albums. The Who were plagued with shoddy production of their albums from the get go and only really figured out how to record well towards the end of their original career when Pete had already written their best songs and wanted out, Keith Moon was badly out of shape or dead, and the band was just grinding on past their prime.
However, as a live band there really is no comparison: The Who was better when they were both in their prime. The difference is even more obvious when they are viewed visually. To be fair to Led Zeppelin, there isn't as much good footage of them playing as The Who back in the day. The Who made their career of playing live, and people in the know who saw them in the hayday circa '68-'76 almost always say the were killing it all times. Sadly I'm too young to have seen either band in their prime, and feel pity for the pathetic sham of "The Who" that is just too tired and too old destroying their reputation as a live band. Led Zeppelin had the good grace to admit is was over and not tarnish their legacy like Pete and Roger are doing.
Even when they felt they had played poorly, hated the gig and venue, and were stoned out of their minds on LSD from having their drinks spiked, The Who played like this at Woodstock:
https://www.youtube.com/watch?v=DdaHT6cGv2U