The decision to buy APs depends on the number of days you plan on spending in the parks, how many water park days you want to have, what type of accommadations you want, how you shop and where you eat. The AP program offers the best discounts. At TWOD store in MP, the AP is the only discount excepted- 10%. If you play mini golf on site, it's 50% off. If you stay on-site & pay cash, AP's offer sizeable discounts. Many great restaurants offer 10% discounts.There is also 15% of on backstage tours. If you normally spend money of these listed items & don't recieve any discounts, then buying the APs can save you a bundle. Most people that buy APs also book their trips to get at least two full trips in during the 52 week life of the pass.
IMO, if you spend your vacation on-property, if you're going to be there more then 10 days during a 52 week span, buy the AP's.
The desicion between AP and PAP depends entirely on how you use water parks & DTD.