I was leaning towards the Fire until I realized that the Nook is the only one that supports Word, PPT, and Excel. This is important for my business. One of the reasons I want one is not just the e-reader function but the ability to use it at shows and events. Also the compactness when traveling.
The Nook does have more space. However the Fire allows you to store your data using the Cloud, so that may not really be an issue.