I do not own a Proto, but the SL has very nice dampness.
The SL is also only a directional board because of it's default setback(If I remember it's 1"). Other than that it has symmetrical flex.
Some on here have said you can just put your bindings on up one notch on the inserts to make it a true twin, but I've never personally tried that as the setback doesn't bother me after I've gotten more proficient in switch stance.
Edit: btw, either board you get you'll really appreciate the sidecut. Boards with multiple contact points make life so much nicer in icy conditions.
Last edited by Bayoh; 12-01-2012 at 10:55 PM.