My oldest 2 have Fires, I have a keyboard 3g w/ad, my husband has the cheapest one and for Christmas my husband got me the paperwhite. I LOVE the paperwhite. Im a night reader who lays in bed reading for hrs and even with my bedside lamp on I had issues seeing sometimes since I would change positions. A week and a few books later Im in love. This thing is awesome. The touch screen has taken some adjusting simply b/c Im sloppy and put my hands anywhere to hold it but its hasn't been that bad.
For reading I wouldnt go with a Fire simply for being backlit and the short battery life. I read hrs a day and with my 3g/wifi off can go well over a month between charges. My daughter has to charge her kindle often when she uses it. The cheapest kindles are great and cheap so I would just buy both if you really want a reading devise and small tablet. I plan to give my oldest my old kindle (or switch it with my husbands) so she can read on that instead.