Question

debate on desert cooler is a better option than Ac in summer prevention of ozone layer

Answer 1

desert cooler is better as I have heard sitting in AC leads to an increase in body fat....

Answer 2

a desert cooler is a device that cools air through the evaporation of water.it can be more advantageous than an air conditioner because, it will simply make our electricity bills increase and also it is a better way to save electricity.
a desert cooler simply is a Evaporative cooling which  differs from typical air conditioning systems which use vapor-compression or absorption refrigeration cycles .
and
i am giving you difference 

IN HUMIDITY 

Air coolers vs air conditioners work in opposite ways to control humidity. Because air coolers take the hot dry air from the room and then cools it through evaporation, they add moisture to a room in the same way that a humidifier does.

ENVIRONMENTAL EFFECTS 

Because air coolers use water as a refrigerant, they don't contribute to any ozone depletion. 
Prior to 1994 air conditioners used harmful CFCs as a refrigerant that were found to have ozone depleting properties. 
You don't necessarily have to choose between an air cooler vs air conditioner. 

Location

Air Coolers need hot, dry air to function properly. Air coolers are better suited for the western/mountain states like Colorado, Utah, New Mexico, Nevada, Arizona, and parts of Texas. 
Air conditioners can be used in places that an air cooler cannot.