The X is magnitudes louder than the S. At least between my cars, the X is somewhere along the lines of three to four times louder. I can hear the X from 100 yards away pretty easily. My S requires being a few cars away in a lot before I can hear it.The S is this way as well.
I parked next to a bike path the other day and used the app to start cooling the car. It was so loud, people on bikes were nearly falling off as they craned their heads to see what the heck was causing the noise.