Need advice on slideshow

1

I dont know wheather to create a new instance of a loader each time:

var loader:Loader;

someFunction(){
loader = new Loader();
loader.load(new URLRequest( url );
}

or reuse the old one and just call load each time:

someFunction(){
loader.load(new URLRequest( url );
}

Second question is (if I use the second way) why do I need to unload the loader before calling load again?
(otherwise I get an error)

it works either way as I figured by I dont know what is better…