I prefer Selling England By The Pound actually. It is most likely because I haven't really listened to The Lamb Lies Down On Broadway enough.

While lyrically speaking, the latter must be superior (and I say that not necessarily out of experience, yet as a consensual statement), the former, in my mind, far surpasses Lamb on musical grounds and instills in me a cathartic feeling with its soaring conclusion much as the conclusion to Van Der Graaf Generator's Pawn Hearts album does; both are very solid all the way through I would say, and function as one long song one may also say--thusly placing them as two of my favourite progressive rock albums.