There’s no definitive answer, it really all depends on the dates, resorts & room types offered for the BB & other discounts. In the past, some dates & resorts were included in BBs that weren’t included in later discounts. Like every other discount, different resorts or room types might be available depending on the dates you’re looking for. IMO the biggest advantage is you know you have a resort & room type you want at a discount, often more than a year in advance. BB also follows the normal WDW change/ cancellation policies. So you can book a BB & change without penalties if a better discount comes along. The only drawback is you have your deposit money tied up until your next stay.