Well, the Lionel IR link is a totally different animal. It is only a one-way link, from the locomotive to the tender. However, being a digital serial communications link, you can carry multiple commands to the tender. Coupler, backup light, marker lights, sounds, etc.
MTH PS/3 has a serial communication link between the locomotive and tender, so control of a lot of extra stuff in the locomotive is easily accomplished with PS/3 steam.