Javascript module template / organization / submodules

Question

Javascript module template / organization / submodules

I would like to know what is the difference (advantages / disadvantages) between the following patterns.
How to create sub-modules based on a module template?

My goal is for my js to be organized into several files that are lazy loaded but have the same namespace.

For instance:

SO.global (global.js) SO.global.registration (registration.js) <- load

var SO = function(){

    var CONSTANT = 'Z';

    function createX(){
      alert("create X");
    }

    function getY(){
       alert("get Y");
    }
    return{
      create:createX,
      get:getY
    }
}();

//SO.createX(); 
//SO.getY();

VS.

var SO = (function() {

    var CONSTANT = 'Z';

    function createX(){
      alert("create X");
    }

    function getY(){
       alert("get Y");
    }

    return {
      create:createX,
      get:getY
    }

} ());