I have everything, and I would say the single edition LOTR and the really nice hardback of the Hobbit. I also add the audio books of both. I never pop the others open at all. [OK, I also have LOTR and Hobbit as ebooks also, from a massive scan and OCR session about 8 years ago…]
I have had LOTR and Hobbit since I was about 8 years old and the peripheral stuff just doesnt interest me. I read them for entertainment, not some deep inner meaning. I dont have the burning need to know why elven sounds the way it does or how it was derived from an odd welsh dialect only spoken on a single small island when combined with old norse. Really, I dont give a crap.