Basically, looking up words will be painful on anything other than the Kindle touch, while taking notes will be painful on anything other than the Kindle keyboard.
So if taking notes is more important to you, I would say get the keyboard model. If looking up words is more important, get the touch model. And if they are equally important, I would say, get the keyboard model and keep something else nearby that you can use for looking up words (Siri works well ).
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