What is the best Kindle e-reader?

When you open up the options menu on any Kindle, along the bottom you can see an estimate of how many minutes left until you finish reading the chapter (great for seeing if you have enough time to keep reading, or if you should stop now at a decent spot), as well as how much longer it will take to finish the book. It also displays battery life, and how many pages you've read out of the total amount of pages.