"new Number(1.23)" vs. "Number(1.23)" vs. "1.23"

programming flash
1 

var a:Number = new Number(1.23);
var b:Number = Number(1.23);
var c:Number = 1.23;

var d:String = new String("abc");
var e:String = String("abc");
var f:String = "abc"

var g:Array = new Array("a", "b", "c");
// var h:Array = Array("a", "b", "c"); creates compiler error - 1137: Incorrect number of arguments.  Expected no more than 1.
var h:Array = Array(3);
h[0] = "a";
h[1] = "b";
h[2] = "c";
var i:Array = ["a", "b", "c"];

trace(a); // returns: 1.23
trace(b); // returns: 1.23
trace(c); // returns: 1.23
trace(d); // returns: abc
trace(e); // returns: abc
trace(f); // returns: abc
trace(g); // returns: a,b,c
trace(h); // returns: a,b,c
trace(i); // returns: a,b,c

Can someone explain the differences between these constructor methods?
When should “new” be used?