Nook vs Kindle

Definitely the Kindle. Amazon offers an amazing service, especially their personal document service's email feature. That is simply divine. Furthermore, Amazon isn't nearly so annoying to use as a non-US citizen. I don't have to use a trick credit card or proxies to purchase ebooks. Amazon just sells them to me, easy peasy.

Disclaimer: I have a first generation Nook and a Kindle Touch. My comments above are however entirely based on the services provided, not the devices themselves. So this is probably more appropriate as Barnes and Noble vs Amazon.