I agree with AboutAGirl. For me ITTOD represents the band's unstopping willingness to try new things and sounds. It might not be on par on their earlier works but I still listen to it from time to time and I enjoy every single track. Also it's got that moody, foreboding atmosphere to it. When I listen to I'm Gonna Crawl it's impossible to not think that in two years this band was going to be no more. Some people could say that it doesn't sound like Led Zeppelin. Well, which of their album DOES sound completely like the others? When they released Stairway to Heaven I bet a lot of people argued that it didn't sound like them...
TSRTS is cool and all but it's nowhere near their best live performances and it's also heavily edited, and doesn't really offer anything new. So my vote goes for it...
It's going to be really hard to choose an album in the upcoming rounds cause you simply don't choose a favorite Led Zeppelin album... >_<