Divers in this area do not have the luxury of dropping bottles off in a location and picking them up later, as in a cave. Currents and the environment mandate that you carry the bottles on you at all times. Having to keep bottles on you at all times during a dive changes the philosophy of technical diving for this region. Buoyancy changes of the bottles as the gas is being used, must be kept in mind. The size of the bottle and the amount of deco gas must be taken in to consideration.
Decompression is another big difference.
Decompression in the Puget Sound takes place in cold open water, either on the main ascent line or your emergency ascent line. You basically climb in the bell, have a set, and deco. The Puget Sounder get's to hang on an ascent line in 43 degree water, usually having to battle large surface waves and strong currents. Gas management and planning is probably the biggest overlooked factor. Bottom times in the Puget Sound tend to be short.