Benefit of setting "setters and getters" if @property is more simple?

The way I understand this is that sometimes you'll want to use a custom function to set your variable, like maybe using an if condition or something. So the benefit would be that you can enhance your property setting and getting. There are a couple of videos in some of the other challenges where Amit does this for setting default values or default arrays for some of the class properties that he sets. As you go along you'll see this more clearly than I can explain in this response :)

duplicated by accident.

Imagine that you want to add objects to an array property. If the property is not initialized you get an error. So in the getter method you can "lazy initialize" the array. Basically you just create one if there is none. For example:

if (!array) _array = [[NSArray alloc] init]; return _array

@property alone saves us the trouble of writing our own setters and getters but sometimes we want to modify one of them, or maybe both. Don't forget to @synthesize the property in case you do so.

Hope this answers your question!