If you want goggles that will never never ever ever ever fog on you just get the JT goggles that have the "thermal" lenses. These are not only going to be fog-free but will also ensure that you will be permitted to play at airsoft events that happen at paintball fields that have restrictions on the types of goggles you can use. Here's where I got mine:
http://www.badlandspaintball.com/JT-...ive_p_321.html