The stock air box is almost always better because ski-doo spends time and money on research for the best performance and to keep the snow out. if you were to go to a k&n style that comes strait off of your carbs the filters are not good enough to keep snow particles out and they can freeze up.
Ive gutted put on one k&N,added sec.2" outside air intake...side pannel intake gets full of snow and no air.and with all baffling inside hard to get to carb's.all cool air the better