While I recently purchased VWL through Disney, it was only because TSS did not have the contract, UY and price that I was looking for. Maybe next week they will, but at the time I bought Disney was better. It simply comes down to what the inventory is like at the time you want to buy. You really do need to study what is offered and particularily pay attention to the last 4 digits of the code that TSS uses...it represents the date that the contract was posted...the good contracts go quickly.
The last and in my mind most important item to check is the ROFR listing..it can usually be found on disboards and it is a continously updated posting so it ususally has around 2000+ posts, so it's easy to find. Go to the last page and look for the latest updated ROFR list and look at what has and has not passed ROFR at Disney. If you are interested in BWV and Disney has consistantly bought all BWV contracts at $86 or less and passed on those at $88, then regardless of what the asking price or agreed price is at TSS, I would not chance a price lower than $88, unless you are a real gambler and would not mind being disappointed.