Yes - VB is part of the
DVC. VB points may be used to book any DVC resort at the 7 month mark.
Why wouldn't someone pay the lower price for VB? Several reasons come to mind:
VB dues are very high. IIRC, there will even be a special assesment/surcharge in 2006 to cover some of the damage caused by the 2005 hurricane season.
Resale prices for VB will also be lower in the future than those for the DVC resorts. For those who do not plan to keep theri membership forever, it is a concern.
As DVC membership continues to increase, so does the competition to book at the 7 month window. Remember, any member at any resort can book at the 7 month window. Unless your vacation dates are flexible and you are willing to stay at any of the WDW DVC resorts, booking at the 7 month window can be frustrating. And will only grow more so as DVC sells out SSR and begins selling the next resort.
SSR contracts are good through 2054 and often come with "bonus points". VB contracts end in 2042.
I'm sure there are more reasons - perhaps others will post them.
Best wishes -
P.S. DVC points can be used for most WDW resorts, but it is a poor economic value to use them at non-DVC resorts.