This system was chosen over chlorine system because of ozone extraordinary ability to effectively purify water without side effects. Ozone is produced naturally by the sun's ultraviolet light. Ozone is the most powerful oxidizer that can be used safely to purify water. Its alternate, chlorine, has been documented to cause illness, irritation of the eyes and nose, swimmers ear, etc. Chlorine is also dangerous to transport and store.
Ozone is clearly superior to traditional chemical treatment.
Just as nature uses ozone to protect life on earth, we can use ozone to protect ourselves from microorganisms in water and air. It is far more cost effective than traditional chemicals. It is safe for bathers and equipment, traditional chemicals can be very hazardous to both. There is no undesirable chemical smell or taste. It destroys organic matter that can cloud the water or stain the spa surface.