I'd lean more toward the Nook, just because it can read ePubs from all the other book stores out there, as well as Overdrive ebooks carried by some libraries. With the Kindle, you're tied in to the Amazon store and library books won't work for you. I have to say that I have a personal bias against being walled in to one device/manufacturer/format.
Before settling on a Nook, I would recommend that you look at
http://www.inkmesh.com/ and
http://ebooks.addall.com/. You might find that the authors you like to read are also available from other book stores, like Sony or BooksonBoard. In all of my searches for authors and titles, if they were available at B&N, they were available at other book stores too. Have you looked at the
device wiki? There are several devices out there that are less buggy than the Nook.
For specific Nook questions, I would post a question over in the Nook forum.