I prefer eInk with good contrast in light settings and the Kindle Fire at night.
Truthfully reading on the EInk for longs periods of times makes me drowsy. I don't know why.
I don't have that problem with the Kindle Fire. They say the HD version is even better for reading. I plan to upgrade mine. Now I use an app on my Kindle Fire that allows me to dim the brightness to a very comfortable setting otherwise I couldn't use it much.
I had plan to get a Paperwhite but after all the issues with it I am now going to upgrade my Kindle Fire instead.