well IN MY EXPERIENCE the MK2 uses an absolutly wonderful system that involves 5 or 6 bolts to loosen, plus a really ugly T bolt thingy which has a threaded head on it. This tends to be all bent from previous owners overdoing it trying to tension a knackered old belt, or trying to tenion it without loosening the hidden bolt round the back of the pump.
MK3 uses literally 3 bolts, one of which has a toothed wheel on it to allow you to set tension with a spanner. OK its no clever self-tensioner system, but it works well and is infinitly easier to adjust.
The yanks have several methods for including the pas pump in with the main serp belt, but I dont really see the point personally when the stock system will work fine for years on end without needing to look at it.