You must try them out and see for yourself. I have had a Kindle from the start and love it. I love that it is not back lit and I do not like touch screens, so the Kindle is perfect for me. My SIL has an Ipad and loves it. So it is definitely personal preferences as they all are amazing!
But I would say don't get too caught up on the free stuff from the library. You can't get every book OR a book when you want it. But I have gotten a freebie and I was happy I didn't buy it. Good luck. ~ Pat