THe pure basalt used in the HP has a better ability to dampen the vibrations that riders complain about when they are going really fast. Normally, you would want a stiffer board to achieve a more damp ride, but the HP maintains similar flex but adds "dampability, dampness, damperocity" (take your pick). Basalt is a type of volcanic rock that they take and weave into a fiber. Much more earth friendly than the harsh resins/chemicals needed for fiberglass.
Wilson tennis rackets use this basalt tech in their high end rackets, because it dampens vibrations caused by the ball hitting the strings, without altering the flexibility of the racket.
So basically, when people say the board is faster, they are saying that they feel more comfortable going warp speed, because the board isn't vibrating as much.
Both versions have the same base. The HP model has the Columbian Gold Core, the regular model has the H-Pop core. The H-pop core is a blend of the Columbian Gold wood and other types of wood not named (I'm assuming it helps bring the price down for the non HP version).