Both units feature motorized touchscreen LCDs (6.5-inch for the 4900, 7-inch for the 5900) and XM and Sirius connectivity, but the 5900 one-ups the 4900 with the inclusion of iPod compatibility and sync-support for Bluetooth phones thanks to an optional CD-BTB100 Bluetooth adapter.
One reason start ups are attracted to information-centric business models is that they offer true leverage given that the labor costs required to generate an incremental dollar in revenue are remarkably low when we deal in ones and zeros.