Re: An honest question
<uninformed-opinion>I have an older Kindle Fire that was used almost exclusively for reading. It's very good for that, but my Kindle is even better (for books that don't use color/colour).
If you expect your PDF's to include color (ah, t'hell wit'it) then I expect a larger Fire would be great; in fact I might think about doing that myself... except I don't read many PDF's. Or if you just need a larger format than the Kindles offer.
</uninformed-opinion>