CPNY, it depends on when you travel, whether you plan far enough ahead, and whether you care which DVC resort you get. Food & Wine Festival is popular with DVCers so those who have points at the Epcot area resorts book their home resorts early and you'd need to book early as well in order to stay at your home resort. But if you tend to plan fewer than 7 months ahead for holiday weekends and the most popular times/events/resorts, you may find little or no availability at the most popular resorts by the time you look. At 7 months out, all DVC members points from all DVC home resorts may be used to reserve stays at any DVC resort, so they book fast at popular times.
Ex., trying to reserve a popular resort at a popular time, like BWV or BCV during Food & Wine, is nearly impossible at 5 months out, even if you points are based there. The home resort advantage no longer exists at 7 months out. If you don't need a home resort advantage (i.e., not planning early and don't care which DVC resort you book), then you don't need to buy points at a particular home resort. In that situation, it makes more sense to get a good deal on a resale at a DVC resort with lowest maint fees.
Offsite is far more affordable (especially the purchase price) but does not have the onsite perks. We are happy staying at Wyndham Bonnet Creek (offsite) for variable lengths-of-stay with our resale Wyndham points from NC & TN home resorts. Not all offsite options offer short stays with points. Not sure how easy it is to get a short stay at Vistana. If you consistently want short stays onsite, DVC is the only purchase option... or you may rent points or a room through Disney with a promo discount. We occasionally exchange into a 1BR at DVC Saratoga Springs for a week. This is not possible if your home resort is a week at Vistana nearby since there's a block on RCI exchanges into DVC from outside resorts in the same region.