Thus far Skeek has the most rational response.
As someone who started out a devout Who fan, and then began appreciating Zeppelin, it's a difficult question to consider. It really depends on the mood... at times the Who can be transcendentally brilliant and compositionally precise; on the other hand the pure and relentless musicianship of Zeppelin is awe-inspiring. I don't want to over-glorify each band, but they've been a standard in my listening catalogue for a long time... and will remain. In terms of direct comparison, there's no point. There's a time in your life for both, and room for more. Why can't we listen to music without keeping score?
Who's better? Who's best? When all is one and one is all. to be a rock and not to roll...
It's all worthy. This thread is demeaning in its best sense.