Kind of tough to generalize on this one. Some people like the Kindle, others like the iPad. I spent 18 months on Kindle 1 and 2 and then went to the iPad and just can't go back. I've used the Kindle 2 or 3 times since I started reading on the iPad and it just doesn't do it for me anymore. I certainly understand that some people prefer the Kindle for reading, but there's no "right" answer for everyone on this issue.
I agree.
I have owned the iPad since day one and enjoy reading with the iBook app. I also use the Kindle app for books not available from Apple.
I just purchased a Kindle 3 special offers model due to the very low price. It is a very nice device and the special offers do not get in the way of reading books. However, it is not for me.
I read two books using the Kindle 3 and missed many of the iPad features. I enjoy the book like quality of the iPad. I like being able to highlight a word or phrase and then search google for more information. (I prefer reading history books so getting more detail or a different opinion is important to me.) The interface is much easier to use.
For me the only things Kindle 3 have to offer is low price, long battery life, and being able to read in sunlight. However, I don't even read printed material in sunlight as the reflection off the white paper is hard on my eyes.
I prefer non-fiction and my wife prefers fiction. She has yet to read an eBook from any device.
Last night I bought from Kindle the next book in the series of fiction she is reading. She will use the Kindle 3 to read it. Then she has a book to read on my iPad. If she likes the Kindle 3, it is hers. If she prefers the iPad, I will give it to her and return the Kindle 3. Then I will buy an iPad 2 for myself.
As you said, it is personal choice.