Cab1L has no antenna and communicates with either a Base 1L or Legacy Base. It is also able to do 99TR (Trains) and transmit Legacy quillable whistle command. It cannot directly communicate with a TMCC Powermaster without an add on Powermaster Bridge.
The Cab1 can only talk to a TMCC base. It cannot control TR past 9 or activate the quilable whistle feature of Legacy engines. It does have an antenna and communicates on 27mhz as opposed to the Cab 1L which is in the 2.4ghz range. The Cab 1 will also communicate directly (without a command base) to a TMCC Powermaster.
The Cab1L was made to function and behave much like a Cab1 when folks asked for a less complicated and less expensive remote.