Do you notice a big difference when your hauling ass between both boards?
How about jumps? I think my SL is pretty damn poppy but I imagine a decent more on the Proto?
Yes, there is a huge difference between the SL and Proto at high speeds. If you are just flatboarding, you can get away with it the Proto, but if you want to do carved turns at speed (i.e. actually snow-board) the dampness is going to help a lot.
Proto is a little bit snappier on jumps - but proper technique slays any fancy tech. Pretty much anyone who complains that their board is too heavy doesn't know how to ollie properly.