The standard hardcover edition, which I purchased, contains a concordance, which is missing in the college edition. The maps are generally the same, however, there is an additional update to the maps concerning the Setting of the Exodus, Roman Empire, and Setting of Early Christian Missions.
One of the immediate areas where the NOAB has been updated is in the individual book introductions. Although I haven't had a chance to read them in detail, each intro is clearly marked and broken down into parts focusing on issues like Authorship, Date, and Place of Composition, Literary Form, Interpretation, Style, Structure, and additional issues pertaining to the book being read. This makes finding particular introductory information a lot easier than in prior editions. One helpful inclusion, for example, I found in the introduction to Ephesians, where the NOAB included a chart documenting the parallels between Ephesians and Colossians. Nice touch!
Throughout the text, there are 40 additional in-text maps, charts, and diagrams, many of which were included in the Augmented 3rd edition. The appendix contains a set of essays covering the Canons of the Bible, various forms of Interpretation from ancient to modern, Cultural Context essays, and a set of tables that includes a historical timeline, table or rulers, weights and measures, calendar, and parallel texts. There is also a glossary of biblical scholarship terms and a complete index to the study materials.
Overall, it seems like it is a very nice update to the Augmented 3rd edition. I have checked up on some commentary notes that had me scratching my head in the previous edition, and for the most part I think they have been improved and clarified. Of course, I have only had this 4th edition in my hands for hardly twenty-four hours, so take that for what its worth. Again, one must keep in mind that this is an ecumenical study Bible that has Catholic, Protestant, and Jewish contributions. If you are looking for a devotional or life application study Bible, don't buy this one. However, if you like your study Bible with plenteous notes on literary forms, historical context, and other modern Biblical scholarship terms, purchase the NOAB 4th edition. It will eventually come in genuine leather too!