Kenny,
CAB1-L is Legacy, but a down sized version of CAB2-L. CAB2 gives you more features, but you can still run TMCC with it. Also, you can run Legacy engines with CAB1-L as well, but you won't be able to activate certain features like whistle quelling. Lionel came out with CAB1-L first then released CAB2-L. For me I prefer CAB1-L because it's a little simpler to operate.
Don't mistake CAB1-L with CAB1. CAB1 uses 27MHz and CAB1-L uses 2.4 GHz just like CAB2-L.
Tomorrow (Saturday), I'm going to be at 'I Love Toy Trains The Country Store' aka TM Books & Video's for a Legacy clinic and to run trains. Should be fun.