First of all, let me assure you that I am not a realtor, nor do I work for anyone who sells timeshares. I'm just a person who has spent a lot of time and effort muddling through all the fine points of
DVC ownership, and have found it to be a complex, technical, confusing place -- and a place where the devil REALLY IS in the details. Disney has done a masterful job of fixing most of the problems with timeshares, but this is still a complex undertaking on its best day. This is not something you should get involved in without a LOT of research, and these boards are a great place to start learning.
The first thing I would urge you to do is to make yourself thoroughly aware of all the ins and outs of DVC ownership. You should know, at a minimum, what the term "use year" means, what borrowing and banking are (and when you can and can't do them, and also what happens when you bank or borrow and a change in plans causes a cancellation), you should know what the annual dues are for the property you're considering, you should know what eleven-month and seven-month windows are (and what they mean in your particular circumstance).
With DVC -- points is points, no matter where you own, and you can use them equally anywhere. Therefore, you may well find that buying a resale makes more sense for you than buying a "new" interest in Saratoga Springs from Disney. You will probably save some money with a resale, but more importantly, you may get
exactly what you want rather than what Disney is selling at the moment.
I think a lot of the decision lies in your particular family situation. We all tend to focus on the costs (and they ARE important), but the most important thing -- IMHO -- is the fit between your family's unique situation and what you buy. The dollars are important, but the long term workability and benefits of your particular BVC ownership are the most important thing.
For example...
Do you have some flexibility about when you take vacation? Do you have the ability to make vacation plans 11 months ahead of time? Seven months? Do you really care what resort you stay in, as long as it is one of the gorgeous DVC properties? (Some people love trying different venues, others have a strong preference for one place) To the degree that you are flexible, can plan ahead, and don't really care which resort you stay in, buying the cheapest points available may suit you perfectly. [Watch out for those pesky annual dues, though. You might see a property which is $5 less per point on the one-time purchase price, but $1 per point EACH year higher on the dues! That's not really cheaper.]
Do you want to be fairly assured of getting a reservation in a particular resort, at a particular time of the year? If so, is that a peak time for that resort? If the answers to these questions are yes, then you should probably buy that resort -- whether from Disney or resale -- provided that you can plan 7-11 months ahead. If you do, you will enjoy the 11 month window when and where you want to be.
In short, I'm not trying to promote either approach, but you would be well-advised to really research all of the options, and really understand the nuances.