たまに知りたいことがあるので、AS3.0のデータ型のサイズを出力しました。

var _uint:uint;
var _int:int;
var _Number:Number;
var _String:String;
var _Boolean:uint;

trace("uint = ", getSize(_uint));
trace("int = ", getSize(_int));
trace("Number = ", getSize(_Number));
trace("String = ", getSize(_String));
trace("Boolean = ", getSize(_Boolean));

trace("Bitmap = ", getSize(new Bitmap()));
trace("Shape = ", getSize(new Shape()));
trace("Sprite = ", getSize(new Sprite()));
trace("MovieClip = ", getSize(new MovieClip()));
trace("TextField = ", getSize(new TextField()));

出力結果

uint =  4
int =  4
Number =  8
String =  4
Boolean =  4
Bitmap =  236
Shape =  236
Sprite =  416
MovieClip =  452
TextField =  1024

AS3ではほぼ意識することありませんが。。