Let us just look back at 1967 and take all of the albums mentioned here as what they are.... snapshots of music and musical culture and their flowering at the time.
It is most definately true that this album resembles Piper at the Gates of Dawn more than Sgt. Pepper. Reasons being, among many others, the strong penchant for improvisational segments and segues, and the rough-hewn production. Sgt. Pepper was more a collection of finely polished vignettes, and finds a lot of it's notariety in the sheer technical arena, as a great many recording techniques were born, and the album changed the way all subsequent albums would be recorded.
This is not to take anything away from ANY of the albums mentioned, these are just some of the facts as I see them.
People mention the arrangements, textures, and Orchestrations both horn and string on Their Satanic Majesties Request, and with good reason. These are all elements that elevate the songs on this album to what they are. Anyone bother to note just who ARRANGED all that, and in my opinion, was largely responsible for a good bit of the sonic results we have? It is none opther than John Paul Jones, of Led Zeppelin, who prior to Zep was one of THE arrangers/orchestrators in the British pop music studio scene at the time. I feel that his contributions on this album in particular cannot be stressed enough.
All that being said, it is a great snapshot of a place and time, and is a musical landmark for all of time.
Happy listening to all.