Disney subsidizes part of the closing costs. With resale you will most likely have to pay all the closing costs.
Disney gives current year points. With resale the contract may have current points, may have banked points, or may have points already borrowed out and used. You really need to understand the point status. On the rent/trade board points generally go for about $10/point. If you compare a Disney purchase that has full current points versus a resale contract that has no current points, you can figure the difference is about $10/point. (Or about $7/point if you just want to 'value' the original cost plus fees.
Disney pro-rates maintenance fees for the remainder of the calendar year. Many selling resale expect the buyer to pay the maintenance fees for the whole year stating 'you get the points'. However maintenance fees are based on a calendar year, not a use year. Many over pay on resale contracts because of this difference.
Disney will have incentives so be sure to compare the final costs.
Disney will finance if needed. With resale you have to pay in full or find your own financing.
With Disney you get to use the points almost immediately. With resale it can take up to a couple of months, depending on how fast the seller completes their paperwork and how fast Disney does their ROFR evaluation.
With Disney you can purchase as many points as you want (beginning at a 160 minimum). If you want 182 points, you can get that amount. Or 190, 205, whatever you want. With resale you can only get whatever the contract being sold has. It is fixed.
There are a lot of differences so evaluate carefully. If buying resale pay particular attention to the number of points (banked, current, borrowed) are in the contract, and also the maintenance fees.
Hope this helps.