What's the difference !!?

What's the difference !!?

whats the difference in performance or any kinda difference between these two??

1.
function Declare(message){
      alert(message);
}
Declare("Hi 1");
Declare("Hi 2");

2.
function Declare(message){
      alert(message);
}
var declaration1 = new Declare("Hi 1");
var declaration2 = new Declare("Hi 2");