The 2600 is more compact, but does not have all of the expansion capabilities of the 3600. The 3600 allows customers to add "pods" to use CF GPS and CF Barcode Scanners. In addition, the Through-the-Box Connection Pod allows customers to run cables through the case for USB, Power, etc. If you want to sync through the case, OtterBox offers a Serial Pod to allow for syncing and power recharging through a null modem serial connection.