As Diane said, what time of year do you plan on traveling?
Other things to consider.....
How long are you willing to wait for the right contract to come along?
Is use year important to you at all? The completely wrong use year at VWL and the perfect use year at BWVs may sway your decision.
How flexible are you on the number of points you are buying?
Are you willing to pay a little more for the right resort?
Is the difference in dues (which is pretty small between these two resorts) important at all?
Do you have a preference on which reseller you go through?
BWV points are generally more available, and generally sell for a little less. So you may have better luck finding a resale contract at a good price with a good use year for you and approximately the right number of points quickly. You may have to wait a little longer and pay a little more for your VWL contract.
I know the advice here is "buy where you want to stay," but if you'd be happy at either of these resorts - you may want to keep an open mind and just shop for the contract and see what comes up.
When we went resale shopping last year, my first bid was on an OKW contract - the important thing to me was quick (I'd made the decision and I wanted it NOW), number of points (actually $$$, I had a little over $10,000 in cash coming as a bonus and didn't want to spend more than that), and a Winter or Spring use year. When that contract was pulled (the seller decided not to sell), we'd been working with Jaki for a few days, so working with Jaki became easy. We ended up with a BWV contract.