I've designed and ridden in cars with a well designed air system. If done right, they will outperform struts/shocks/springs due to what's called "exponential pressure" (I believe that's right) which means as the car goes lower on a pressurized bag, the bag carries a densier amount of air due to smaller volume to fill.
Something like that....but yes, I've seen Rally and Auto-X racers use Air-assist struts because they can tune them on the fly, from the driver's seat.