As mentioned biggest advantage time addon available immediately resale takes a long time with ROFR, closing and getting into the system.
Two other advantages:
No closing costs on an add on from DVC (on a small contract closing can add considerably to the $/pnt on resale)
Depending on use year the current use year points & maintenance fees MF can also enter into the equation. If available Oct & Dec use years from DVC would still have all their 2007 pnts which they would let you bank. (all other UY would have all their 2008 pnts) You would only pay the MF for the portion of the 2008 year after your purchase date.