Tough one, but Led Zep for me overall, although certain DP tracks I rate possibly higher than anything the Zep did.
I guess being a blues fan, the stronger influence of that in LZ's music is what turns the trick for me. and is also the reason that "Lazy" by DP is a firm favourite. I like the folk influence of LZ too. But I also think that Page was a sloppy guitarist - he gets away with it because blues doesn't have to be note perfect perhaps. But if you put a guitarist with perfect intonation in LZ, I don't reckon it would work the same.