SL has a flatter highback, similar to the contact pro. Also has an assym ankle strap. Is there something you wanted to know specifically?
It's an Asymmetrical-Symmetrical highback easy to roll in hard to roll out.
Forgot about the asym straps.
youtube search has a good overview of both. Internet, all-around, nice guy spenser says the force is the most responsive binding in the lineup, that's under $250
Due to the baseplate the SL is probably between the atlas and the force as far as response goes.