There are several reasons why most of us say that you should "buy where you want to stay".
The first is the fact that you get an 11 month window at your home resort v. the 7 month window at other resorts. If you travel at peak
DVC periods (which are not the same as the peak periods for the non-DVC resorts), this window is very important. It also matters if you want something that is limited like a GV, a standard view at the BW, a room at HH during the summer, WLV during Christmas, a 2BR w/ 2Q beds at BCV, access to SAB, etc...
Secondly, there is no guarantee that you will always be able to book at a resort you don't own. The more DVC grows, the more people will be competing for a limited # of rooms. This especially applies to the smaller resorts, which have less availability to begin with. Also, in the event that DVC were to sell off one of the resorts, you would no longer be entitled to trade into/ out of that resort unless a specific arrangement was made.
Third, there is the dues structure. Just because a resort looks like it's cheaper when you're buying in (Ex. - VB), you may pay more in the long run through dues. In the long run, it will cost you more to own at VB and trade into an onsite resort than it would have cost you to buy onsite in the first place.
The last thing I can think of is length of contract. Some people like that they are buying a longer contract at SSR, although that isn't a selling factor for us. I would rather own for a shorter period of time, and be able to stay at the places we really love - and if my membership ends at 74, instead of 87 I'll be glad to have my great grandchildren purchase a membership we can mooch off
