There are still plenty of people who don't like the idea of using a Kindle at all, and there are already a few who have become such fans of them that they're almost giving up on books altogether. But for most people, which is better probably depends on where you are at the time - and the best thing is to use both.
A KIndle is great to read on the beach or outdoors generally - no problem with pages fluttering in the wind, you only need one hand to 'turn the pages' and, especially with the new versions like the Paperwhite, there is no problem with glare from the sun. They are also very good for travelling as you can have as many books as you like on one small device.
But you can't get all books on a Kindle yet, and also you can't leaf through or go to the end or back to the beginning in quite the same way. There is also something special about the feeling of holding a book, so few people would want to give that up.