To start off with, The Beatles and Led Zeppelin weren't quite from the same era, but it was close. The Beatles released their first full-length album in the U.S., "Introducing the Beatles," in January of 1964. Their last original album, "Let It Be," came out in May of 1970. Towards the end of The Beatles' career, Led Zeppelin emerged, releasing "Led Zeppelin I" in 1969. The Beatles split up shortly before "Let It Be" hit stores, but Led Zeppelin continued on to release eight more albums, ending with "Coda" in 1982. As you can see, there really wasn't very much overlap between the two timeframes, but, well, I don't really care.
Now I'll get to the actual comparing. The Beatles started off in the early 1960's as a softer rock group. The sappy love song craze of the 1950's hadn't quite worn off yet at this point. Their first few albums consisted of poppy love songs, much like those of the '50's, such as "Love Me Do" and "I Want to Hold Your Hand."
Their fanbase mainly consisted of teenage girls who just couldn't get enough of the sappy songs. The Beatles continued releasing similar albums for a couple of years, with titles such as "A Hard Day's Night," "Ain't She Sweet," "Help!," and "Rubber Soul." They eventually developed a strong position for themselves within the love song genre.
Then, The Beatles began a change. Starting with "Revolver" in 1966, they steered away from the short, poppy love songs. Their aim shifted towards more energetic and meaningful songs. Album after album, they kept sounding less like the Beatles they had made themselves into. Finally, the real turning point was "The White Album." Unlike anything they had released, "The White Album" was a refreshing mix of...