platinum is stiffer, lighter, and looks WAY sicker. Plus, if you're getting the Platinum Absolute, they throw in a second pair of bonus short fins... just because they're crazy like that
Platinum boards have two hollow fiberglass rods that run down the board that are capped off at the ends. The air trapped inside the rods can only expand so much...therefore giving the board a much snappier and poppy feel to it. SICK!!