This is actually more of a Barnes and Noble vs. Amazon debate.
And in my experience, Amazon wins hands-down.
You see, we bought a Nook the day after Thanksgiving because I thought I wanted one for my birthday. I then decided I didn't really need it, so we refused the package and it was sent back for a refund, which was all ok'ed by the Barnes and Noble customer service support team.
That was two months ago, and we have yet to see the refund from Barnes and Noble after repeated emails and answered questions.
Amazon refunded our initial Kindle purchase very promptly, after we accidentally ordered it back in 2009. They have also replaced our [self]-broken Kindle. TWICE.
I would say if you are in the neighborhood for an eReader, go with the Kindle.
And as I write this, I'm contemplating buying a Nook color. But it's half-price.