It should be a draw, because the differences between the two balance each other out.
I'll name a few:
DUDE, this is straight up correct, the best way to explain a pink floyd vs led zeppelin thing, although in the end i would choose floyd but i still agree with you
The impressive thing for me with Led Zeppelin was how fast Jimmy Page was able to put it together in a summer and by the end of the year had a new album, and having this crazy-Beatles like schedule of touring and recording, and that's where Page as producer could work all that out while they were on the road, and when they wanted to just record at their leisure, he borrowed the Stones mobile studio and wired up Headley Grange.
Pink Floyd were given creative freedom, and I guess as long as they were selling albums that made it in the top 10, could keep going. Atom Heart Mother charted at #1 because Ummagumma had done really well, and peaked at #5. Not bad for a double album.
Funny thing - "Dark Side of the Moon" peaked at #2 in the UK, #1 in the US. "Animals" didn't peak at #1, either. "The Wall"? #3 in the UK, #1 in the US. "The Final Cut"? #1 in the UK, #6 in US.