Regardless of how many points you buy, don't buy a 600-pt contract. Break it up into smaller contracts at different resorts (choose your top 3) so that you have lots of flexibility. You could still do your 14-night trips, but you'd just book two reservations and have a split stay.
Depends upon whether one really wants the multiple resorts or not AND/OR is willing to deal with a split stay. If Kidd wants VWL every time, I say buy 600 points at VWL.
As for the size of the contract, that's not necessarily a deal breaker. The main benefit to owning multiple contracts is that a portion of the points can be sold off at some later date.
However, the benefit of buying such a large resale contract is that the prices tend to be significantly lower. If I were in the market for 600 points and there were listings at $60 pp, there's no way I would pay $65 per point to acquire three 200-pt contracts. I'm not paying an extra $3K--or any noteworthy dollar figure--just for some added back end flexibility which I may never even need.
Pay the lower price up front. Worst case is you may have to list for sub-market prices years down the road when trying to sell. Maybe. Possibly. And even if it comes to that, you paid sub-market to begin with so it's a wash.