When I read the title I assumed you were going to say Led Zeppelin, because everyone always says that. But I completely agree with you. I can't say I've heard every song by both, but I have 3 Deep Purple LP's and the Cabala 8 disc collection by Led Zeppelin, so I'm pretty familiar with their work. Especially the early 70's stuff is clearly in favour of DP.
Frankly there aren't many songs by Led Zeppelin I like, even Stairway to Heaven I find overrated. The whole band is overrated if you ask me. Anyway, Purple it is.