The nook allows you to utilize Overdrive, the system that allows you to DL books from public libraries to your computer and put them on your Nook. I dont believe this is an option for the Kindle.
I am waiting for them to lower the price of digitized books before investing. I really dont see much point to spending so much on an e-reader and then having to pay the same price (or more) than a paperback book to DL one.