Do you prefer a kindle fire over a nook color and why ?
I'd go with a Kindle fire. You get complete access to the Internet, you can download many apps, books, movies, etc., plus it's run by amazon which has a lot of similarities to iTunes, so it is very easy to use.
Between a Kindle Fire and a Nook, I would go for a Nook tablet. It has a better screen, twice as much RAM and expandable storage space as compared to a Kindle Fire.