Can you explain the difference?
I think it's better if I don't know.
I think I'm better off not knowing.

Question

Answer

The second sentence makes it clear that it's better for me, whereas the first one doesn't.

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I think they are about the same, but the second has a stronger, more ominous tone.

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What about these ones? "I think it's better for me if I don't know" or "I think it's better for me not to know"

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I'd say they are the same.