Buy where you think you'd enjoy staying the most. When DH and I were buying in 1997, the only 2 resorts available were OKW and BWV. OKW was overall a little cheaper. We looked at both, and while we enjoy the Boardwalk location, we also liked the laid-back atmosphere of OKW. We asked ourselves"If we could only stay in one reosrt for the next 45 years, would we be happy at OKW?" and the answer was yes, so we bought there.
BWV is a great location. In addition to being right on the Boardwalk, you have Epcot and MGM within walking/boating distance. It's an overall lovely resort, with nice pools, some lovely views(which will cost you extra points!),nicely decorated.
SSR is an unknown, but we do know that DVC properties do have a ceratin level of quality, so there's no worry there. You will be close to DD...there's wil be little boat that will take you there, I think, and it's also walkable. You will be near some great shopping, golf courses, and a very nice spa. The artists' renditions of the pool look spectacular, there will be a viewing area for the DD fireworks. All in all, sounds great.
Another poster brought up a good point to consider...your age. You get the extra years at SSR, but what good will they do if you're 90 and can't go???? Of course, they are willable, so if you have someone to will them to, that solves that. Even if you can't go when you get older, if you have kids, they'd probably make use of them. Of course, if something changes dramatically in oyur life where you think you wouldn't be using the points, the contract can be sold.
Remember, your home resort will give you an 11 month booking window, and the other resorts will give you a 7 month booking window. At certain times of the year, that can make a difference.
What do you like to do at WDW when you go? What do you think you'll enjoy doing as the years go on??? All of these are quesitons you should ask yourself. Keep in mind though, that there really isn't one property that's any nicer han the others. They are all lovely in their own way, each with their own charming characteristics. Really, what you have to decide is what characteristics of what resort best fit the characteristics of the type of vacation you want to take.