see http://www.synthzone.com/ubbs/Forum25/HTML/001555.html for an answer. The 2600 has the new 8 part accompaniment with 170 styles but no custom section. The big thing at this price point so far as I can see is the ability to record digital audio and put digital audio on the card with the CB7 kit and play it from the 2600.

The yamaha direct disk access is a good feature but my personal downside is being distracted by the noise of the floppy spinning for a minute when you put it in while you are trying to play.