Led Zeppelin is by far the better group. I support this statement with two simple reasons.
Firstly, the members of Led Zeppelin were more skilled at their respective instruments than any of the other musicians in question. For example, there's no comparison as far as guitarists go; Jimmy Page easily "out-played" George Harrison, John Lennon, David Gilmour, Syd Barret, etc. Where vocals are concerned, none of the Beatles were anything very special (John Lennon himself stated many times that he disliked his voice). The members of Pink Floyd were not notable singers either. However, Robert Plant has made such a name for himself in rock (undoubtedly because of his ridiculous range and many different styles of singing) that he is constantly rated to be at least in the top ten if not the number one rock vocalist of all time. When it comes to drumming, let's face it: Ringo Starr wasn't really that good, and Pink Floyd's drumming is nothing memorable. Ask anyone who listens to Led Zeppelin though, and they'll tell you how great a drummer John Bonham was, especially because of his powerful but technical drumming. In fact, it was he, along with a few others (like Ginger Baker, for example) who brought drums to the forefront of rock. Lastly, John Paul Jones (real name: John Baldwin) was a fantastic bassist as well as an accomplished composer, mandolinist, and keyboardist, helping to start the late seventies and early eighties fascination with synthesizers and keyboards. Actually, every member of Led Zeppelin could play multiple instruments, and play them extremely well. Then there's lyrics: while Lennon/McCartney were fantastic songwriters, Page/Plant were arguably just as good or better. Pink Floyd's lyrics don't compare to either of them. (By the way, this past paragraph should explain why some people like the Beatles or other bands more but think Led Zeppelin is better.)
Secondly, Led Zeppelin has the best variety of music. Here's a few songs just to give you an idea of all they could do: "Fool in the Rain" - samba; "D'yer Mak'er" - reggae; "Going to California," "That's the Way," "The Battle of Evermore" (as well as much of their third abum) - folk; "Since I've Been Loving You" - slow blues; "Carouselambra" - progressive rock; and let's not forget their basic down and dirty blues rock songs like "Bring it On Home," "Whole Lotta Love," "When the Levee Breaks," etc. Also, "Stairway to Heaven" anyone? It's the most requested song on American radio and it is often hailed as the greatest rock song ever. Led Zeppelin purposely mixed in all these different styles and influences to push the boundaries of what we call rock. Their only so-called stain (which I'm sure people will end up complaining about on here) was the accusation of stealing music. However, as one would find after research and listening to many songs supposedly stolen from, Led Zeppelin's music was entirely original and their lyrics were only very rarely similar to those of other songs. And, when they were similar, they were in homage, seeing that the members of Led Zeppelin were avid American blues fans.
I'm not even going to go into live shows, where the Beatles played for thirty minutes, Pink Floyd an average length, and Led Zeppelin sometimes up to four hours! (The members of Led Zeppelin were also great performers, utilizing movement, clothes, and special effects to stun and wow the crowd while never taking any importance from the music. Pink Floyd should have learned to do that.) And I'm also not even going to go into Led Zeppelin's good management by Peter Grant and Richard Cole (their tour manager, to be specific.) Oh, Led Zeppelin made their own record label as well, their most famous client probably being Bad Company, a very good band.
Obviously, Led Zeppelin is the best of the three and, in my opinion, of all musical groups of all time. It just comes down to a matter of preference concerning each band's music. Fortunately, they are all incredible and, unlike the music artists of today, will most likely last forever.