If you are going to pay cash, there should be no difference at all. The end date for
DVC is January 2042 regardless of which resort you buy into. So you will get 40 years whether you buy from Disney or resale.
When looking at the resales, look to see if the seller has used any or all of their current points, whether any are banked into the next year(or this year) or whether any are already borrowed. This will help you determine whether you are getting a good deal.
When we bought our resale last Oct., there were 2 contracts for the exact same $ amount. One was the same as our HH use year (Feb), but they had used all of their 2001 points and borrowed all of the 2002 points, which meant that we wouldn't get any points without borrowing until Feb 2003!! The other contract had banked points from 2000 and all of the 2001 points, although the use year was different from our HH contract. We went with the second one because it was the better value for us.
One other thing I would like to point out is that with resale you will probably have to pay for this years dues, where through Disney, it would be prorated. However, this is always negotiable with the seller.