It's important to watch for careful wordings: 22% of sales, 5 million downloads.
As a single data point, I've downloaded about 20 free books (I've read The Invisible Man and I'm halfway through Pinocchio). The overlap of free books on Kindle vs iBooks is pretty high (mostly all from Project Gutenberg).
I think the iBooks ability to download a free sample (usually first 30 pages) is the killer difference. I've downloaded a few samples when I first heard about a book, and every time I open iBooks they're there reminding me about a book I wanted to read, that I can pay for when I'm ready. Maybe the Kindle device has a better "shopping list" type feature, but all Kindle book purchases on iPad have to go through the browser.
I think iBooks is a better service, but the huge Kindle catalog will help Amazon. For a single book, the programs are similar enough that I'd just buy it from the cheaper store.
I have iBooks, BN eReader, and Kindle on my iPad. I primarily use the Kindle. I use iBooks to put free ePub books on my iPad. I bought an Alastair Reynolds book on the BN app, but I'm leery about it's need to "call home to the mothership" every time I open it. What's going to happen on the plane?
I bought the book from BN instead of Amazon because BN's book was $4 cheaper.
It is also highlighted on in-Kindle store page for every book. As has sold me more books by new-to-me authors than any feature on the device.
They have one implementation feature that warms the cockles of my conversion-optimizing heart, right at the end: "Enjoyed the sample? [Buy Now] or [See details for this book in the Kindle Store]" Not only is it one click ordering, I'm 99% sure that they're A/B testing that call to action.)
My only gripe is that if you buy the book, it starts back on the first page, which is a pain because you're an arbitrary length in the story and getting back to where you were using Kindle navigation leaves something to be desired.
As a single data point, I've downloaded about 20 free books (I've read The Invisible Man and I'm halfway through Pinocchio). The overlap of free books on Kindle vs iBooks is pretty high (mostly all from Project Gutenberg).
I think the iBooks ability to download a free sample (usually first 30 pages) is the killer difference. I've downloaded a few samples when I first heard about a book, and every time I open iBooks they're there reminding me about a book I wanted to read, that I can pay for when I'm ready. Maybe the Kindle device has a better "shopping list" type feature, but all Kindle book purchases on iPad have to go through the browser.
I think iBooks is a better service, but the huge Kindle catalog will help Amazon. For a single book, the programs are similar enough that I'd just buy it from the cheaper store.