It's the technology (though our training is probably also higher quality as well). Definitely not the size. Take for example, the chameleon suit. Changes color to blend with whatever environment your in at will, absorbs infra-red light (so anybody using night vision goggles will have a hard time seeing you) and it can also adjust its outer temperature to match the weather, while keeping you warm or cool inside, which makes thermal sights in tanks or other armored vehicles useless for spotting you. To top that, the goggles that are equipped in the helmet are able to see vapors rising up from hollow ground...probably where charlie buried a land mine 2 days ago.
Now you know how good that is, just wait until 10 years or so from now before the realy good technology that we have right now becomes de-classified.
(those who wonder how the CIA knows so much about whats hidden in iraq's backyard without telling you how they know its there...ever bothered to wonder what kind of classified technology they have 22,300 miles up in the sky right now?)