As I have pointed out in previous posts the real reason chlorine dioxide is used over chlorine is because chlorine dioxide is 10 times more soluble in water than chlorine gas, and is a more effective oxidizer.
Here is a list I found of other advantages:
Strictly as a disinfectant, ClO2 offers the following advantages:
• Its bactericidal potential is relatively independent of the pH at between 4 and 10.
• It works better than chlorine for treating spores.
• It needs little contact time.
• It is quite soluble.
• No corrosion is produced at high concentrations, thus reducing maintenance costs.
• It does not react to ammonia or ammonium salts.
• It improves coagulation.
• It is better than chlorine for removing iron and manganese.
As I have also pointed out in previous posts, chlorine dioxide is not very stable and DOES NOT remain as chlorine dioxide when reacted on by other things such as sunlight or water: