I'd say Lord of the Rings, if you can manage to gnaw through the wall of text. It's heavy reading. Harry Potter, on the other hand, is a fairly easy read and Rowling is a talented writer.
Regarding settings, I prefer LOTR. Tolkien was so very dedicated to the details of his creations.
Regarding reading value, well, the wall of text killed me while I've read the HP books a couple of times.
Regarding the movies based on the books, well the Harry Potter films fail if you compare them to the books. The LOTR films miss out on a lot too, but is, in my opinion, a greater visual experience.
So Lord of the Rings, I guess.
Ash nazg durbatulûk
Ash nazg gimpatul
Ash nazg thrakatulûk
Agh burzum ishi krimpatul