I went through a similar process looking at all the options
Chose to go with the Nexus 7 tablet instead as I can choose to use the Kindle app or any other reader app I wish
Plus I can read comics on it, at the moment have vintage Popeye comic and in colour !
Happy with the Nexus 7 and suprised that I don't get eyestrain with it, I use the sepia setting in the readers
I came very close to getting a PW though
Best of luck in your decision making !