We first made an offer for OKW resale, then a month later called DVC to buy a smaller BCV contract. Interestingly, they closed the exact same day. Overall expense was less on OKW, but buying from Disney was definitely less stressful -- able to make reservations almost immediately, they were so clear on when and exactly how everything would happen, and they paid for overnight mailings, etc. so there was no doubt of the exact closing cost. (I have noticed that some people who buy resale tend to multiple the number of points purchased by the difference in basic price per point and consider that their "savings" but closing costs, payment for dues, overnight mailing, wiring fees, etc. make the cost through resale more than that simple figure would yield.)
Depending on the size of the contract there could be a significant difference in price. If I were buying a large number of points I imagine resale would be the only logical route, but for a small initial purchase or add-on DVC definitely gets competitive with the overall cost. For instance, when we bought directly from DVC we got the points for 2002 without having to pay dues for that full year, only tiny pro-rated amount. Again, no closing costs, no other costs at all.
I would not hesitate to go resale again, but also would not definitely rule out purchasing direct from Disney depending on their incentives and other circumstances at that time.