Object factories vs. instances

stuff.js

var Client1 = function(args){
  var prop1;
  var prop2;

  return {
    prop1: prop1,
    prop2: prop2
  }
}

//Same as
var Client2 = function(args){
  this.prop1 = '';
  this.prop2 = '';
  this.prop3 = '';
}

//Cannot be extended using prototype
var clientInstance1 = Client1();
//Can be extended using prototype
var clientInstance2 = new Client2();