The current '10 Nat's sign ups has 11 P-Limited Sport hydro drivers and 8 P-Sport drivers. P-Limited uses an inexpensive spec motor and has been more popular than P-Sport Hydro for many years now. It always pulls more drivers as almost everyone that races FE has a P-Limited Sport Hydro setup.
In years past (and probably this year), most racers use their "smaller" P-Limited Sport Hydro hulls and race them in P-Sport. I'd say 80% are racing hulls that are too small, including me. Product selection has been thin for an adequate P-Sport hull.
Things are changing right now, though. There are 2 new Sport Hydros that are 30" hitting the market this summer with tons of potential. They are targeting the P-Limited market, but P-Sport will benefit as well with these new designs.