I would never recommend buying an annual pass based solely upon the discounts. Buy it if the number of park days you will spend in the parks over the course of a year make it economical.
That being said, there are different perks availableto AP holders that aren't available to non-AP holding
DVC Members.
For instance, seasonal room discounts at regular WDW (non-DVC) resorts..and AP disocunts
can be better than the DVC discount for cash nights at DVC resorts...that depends upon season and discount availability.
AP holders can buy the Disney Dining Experience Card for 20% off at almost all Disney ower table service and buffet restaurants, as well as adult beverages. DVC owners can not get the DDE card unless they are also an AP holder or a FL resident.
Many if the non-DDE dining discounts are the same for AP and DVC, sometimes AP discounts are better, sometimes DVC discounts are better...it varies.
AP Holders get some shopping discounts that DVC owners don't get, like 10% at World of Disney (minimum purchase required)