If they cannot smell you, they cannot find you. And regain control of your backyard. The insects are drawn to the unit where they are quickly and quietly electrocuted. Dispatched mosquitoes fall into a collection tray from where they can be cleanly discarded. Repellents simply smell bad.
Insects avoid repellents and look elsewhere for prey.
It is also quiet and easy to clean. Very few competitors are sufficiently confident about their product to offer this type of warranty.