The motion control floodgate adjustment on the SL in internal. You have to pull the little tab off and use an allen key to adjust. The Race has an external brass knob to make the adjustments to. The race has the poploc option. Other than that, I think the only other difference is a different crown.
What is the price difference? I upgraded my bike this season and got the Reba Race Fork. I don't know tech stuff about bike parts, but the shop I bought it from recommended that fork for me for my size and for racing.