The GRX-CI-RS232 is the RS-232 interface for the NTGRX-3108 and the GRX-IRI is the infrared interface.

The GRX-IRI is about half the price of the GRX-CI-RS232, provides a place for an infrared 'mouse' emitter on the front of it, and is meant to be hidden away in a wallbox somewhere. It provides full control of each zone independently as well as scene control. Although IR is generally less preferable than RS-232, it is my preferred choice with the Graphic Eye. All of the codes are readily available and it is simple to set up just like any other component on the Pronto.

The GRX-CI-RS232 provides some additional programming capabilities and RS-232 is inherently more reliable than IR. The codes are available in the manual that comes with the unit.