The main advantage of the L-1 relative to the H-1B is that there's no lottery so the U.S. company can sponsor you for an L-1 at any time. The main advantages of the H-1B relative to the L-1 is that it's transferable from one company to another and can be renewed indefinitely if you are in the green card process. Regarding which one is better from a green card perspective, the response is that your underlying status has no bearing on your green card options so both are fine.