Reading outside in the sun seems to be one of those things Kindle does better but I live in North Carolina and never ever read in the sun. I read at the pool under the shade of our pool house, on our porches, sitting under trees but can't imagine sitting out baking in the sun and reading. I do know there are some who come to our beaches and do this occasionally but its it something I don't recommend or do LOL.
I am 72 and had cataract surgery about 2 months ago but have 20/20 vision and only need reading glasses. I use several reading apps (Kindle, Nook, Overdrive, Stanza, Bluefire) and read a LOT, using the night mode in apps at night, in bed, but preferably sepia in apps during the day. I carry the Ipad with cameras hiking, urban walking, etc so find myself using it for research, photo review, reading in many places and though I tried the Kindle and Nook found I actually liked reading on it better (I've had mine over a year). I'm used to using backlit monitors since I spend time in Adobe Lightroom and Photoshop and don't find it particularly tiring though others might. Its personal. I do like to read hands free so use a PropUp at homel,put it in Apple (gen 1) case or Dodo case for carrying with me.