Stiffer skis are for more experienced more aggressive riders, while soft are for less aggressive riders. Thats for carving. For park, stiffer skis help stability at high speeds, make for somewhat easier landings, easier presses on rails. Softer are a little less stable at high speeds, but you can do butters and presses on the ground with them much easier. Thats skis anyway. Im sure alot of that goes into boarding.