Yes, you are correct on the contract expiration dates. Advantage: SSR.
If you are going into this with a clear preference for one resort over another, then you should definitely buy your points at that resort. Some folks just love (for example) the Boardwalk and want to stay there 80+ percent of the time. If that's you, then buy at BWV (or whatever your resort of choice might be). You can book your "Home" resort up to 11 months in advance, giving you a much better chance of getting the room you want during high occupancy periods (which tend to be October through December plus the annual Spring Break weeks.)
However, if you've looked at the
DVC material and don't have a clear cut resort preference, then you might as well just buy at SSR. We are owners at SSR. We've had wonderful success booking the other resorts in the program and have no regrets over our decision to buy direct.
Financially, the numbers are very close. In order to get a resale through Disney's Right of First Refusal, you'll probably have to pay $72-74 per point, plus current year's maintenance ($4) plus closing costs ($3-4 per point). That's about $80 per point resale vs. $85 per point at SSR with the 12 extra years.
If you can find a resale with banked points, that represents an additional financial bonus for resale not included in the above. But offset that with the time and energy that you will expend in looking for a resale, making an offer, haggling with the owner, waiting on ROFR, closing, and so on. IMO, it depends on how anxious you are to seal the deal vs. how much time and energy you want to expend to reduce your up-front costs by going the resale route.
Also note that if you go the resale route you will have to pay cash or secure your own financing.
Good luck and don't be afraid to ask additional questions.