The Kindle Paperwhite was my first e-book reader so I can’t compare it with a previous one I owned but, I presently own an iPad with retina display and I can tell you this : the comparison is impossible. Its two different world. The Paperwhite is like a book and the iPad is like a computer in terms of viewing.
You can bring the Kindle at the beach and read your book in the bright sunlight without any problem at all.
“The Kindle Paperwhite boasts the best screen we’ve seen to date on an e-ink e-reader. The built-in light is great for nighttime reading, and the touch screen is a notch above the competition. Amazon’s e-book selection remains best in class. Battery life is excellent so long as you turn Wi-Fi off.” – CNET Review
Also, it’s very easy to download books and to manage them via Amazon!