Jerry A,
Although I am pretty new to Legacy and have never owned the Cab1 L what I have learned is that the Legacy is an upgraded TMCC Cab1, Legacy will control everything the TMCC Cab1 L does with the addition of speed control and other operations. Also with the Legacy you get programming modules for entering your engines into the Cab2, where the TMCC Cab1 one must be manually entered in a different manner. I am sure MartyE will be able to expand on this, he is kind of the TMCC/Legacy guru here on the OGR.
PCRR/Dave