With a few exceptions, demos are genial curiosities, adding context but little else to the standard version. You don’t hear the song any different after.
This one is an exception. Like a lot of folks, I’ve always found this song from Walls and Bridges particularly haunting, given where John Lennon was in his life (and vis a vis the music business); but this version really got me—the break at 3:36 is just amazing. Go listen. (h/t to Stephen Kroninger)
(Stray thought: it might be fun to compile a list of truly essential demos, ones like “I’m Looking Through You.” Put ’em in the comments.)