I have used an Ipad Air with app, but I prefer the Kindle Paperwhite, because it is lighter, the e-ink is easier on the eyes, and the screen size is just right for me, not too small and not too big. I also never worry about the battery being dead. The weight difference is huge compared to an Ipad when you are holding it to read on a long flight.

I still use a tablet or laptop as well, but the "Kindle" still earns a place in bag most of the time and is my go too device for reading.