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Turns out, I haven't written anything here yet.
I read both.
I'd rather read "The Lord of the Rings" 10 times than read "The Children of Húrin" once. It's just awful.
There's too much dreary "sublime" stuff, like the Great Staircases and all that, everyone is doing some nonsense because they were told to by the Valar (the gods in that world), that what is written in fate cannot be changed, and all that other nonsense.
I think the same will be true of "The Silmarillion."
There's much less of that in "The Lord of the Rings."
Added after 20 minutes.
And in general, "The Lord of the Rings" is noticeably better than "The Children of Húrin." It's more interesting, richer.