Private variables vs instance properties

Hi, this is more of a question than issue but can anyone explain why you might want to create errorNotice as a private variable in the first version of this module versus as a property on the instance in the second version? It seems in the first version you have to clean up the private variable whereas in the second version it will be removed when the instance is destroyed. Thanks!

```
// First version
app.core.define('#error', function(f){
var errorNotice;

return {
init: function(){
errorNotice = f.find('#alert')[0];
},

destroy: function(){
errorNotice = null;
}
}
});

// Second version
app.core.define('#error', function(f){
return {
init: function(){
this.errorNotice = f.find('#alert')[0];
},

destroy: function(){
// No longer need to null-out errorNotice
}
}
});
```