OC, I haven't seen Sony or Iliad, but Kindle is wonderful. It's easy to read (you can change the text size, and the contrast between letters and background is such that you can read the page in strong sunlight) and easy to carry (shape and size and weight) and easy to turn the pages. It holds 200 books at one time, and you can order the books downloaded to the Kindle in a second or two, without wires.

OC here are some websites that may help you decide:

 

Compares Kindle to Sony 700

Compare different Sonys

Compare Sonys and Franklins