Progressive in itself is a melting pot of genres. Diversity doesn't always mean creativity. and Pink Floyd did not start Psychedelic rock. They were really only psychedelic rock in their earlier years too. They branched off to progressive rock. Creativity is not in how many labels you can apply to it. Led Zeppelin was generally typical blues bass lines with a solo. Of course, I'm generalizing, but Pink Floyd's lyrics were also quite creative as opposed to Led Zeppelin's generally generic Lord of the Rings inspired songs. Pink Floyd make frequent use of imagery and symbolism in their music and it can get quite emotional. Take for example, The Wall. If you have listened to this whole album you can't honestly tell me you didn't want to cry by the time "Goodbye Cruel World" came around. That leads me to another point. Concept albums. Look at Dark Side of the Moon, all of the songs had a specific theme such as money, death, life, etc. It's also funny that you mention experimentation as a reason that Led Zeppelin is more creative. Pink Floyd started out as an experimental psychedelic rock band. Try listening through the album "Piper at the Gates of Dawn." I don't believe in "better/worse" bands, however I do greatly prefer Pink Floyd to Led Zeppelin (which i still enjoy).