I was in your exact situation last October.
We own VWL and we wanted to add on points to stay at BLT or VWL. We visit MK at least 60% of the time on our vacations so we have no interest in non-MK area DVCs (we tried OKW, BWV, and AKV and they weren't good enough to overcome the bus ride to MK). I wanted either an SSR or a BLT contract instead of another VWL due to their longer expiration dates.
We are going to use the points in the last week of August which is a low demand time. We are going to stay BLT 1 BR Lake View which is the easiest category of BLT to book at 7 months. So we would be a good example of buying SSR and staying at BLT. However we decided to buy at BLT. Why? Because I don't know what the future holds. I want to stay at BLT and with the 11 month booking window I will be happy every August when I go to BLT. If I bought SSR there may have been a trip or two where I couldn't get an entire week at BLT. So that would tick me off. I don't want split stays. I want to stay at one place for a full week and I want that place to be BLT or VWL, so I own at both.
If you are willing to stay anywhere but would "like" to stay at BLT then buy SSR. If you would be upset or disappointed if you didn't get BLT then you need to buy there.
In 2008 there were only five DVC resorts (OKW, SSR, VWL, BWV, BCV). Now there are 9 (OKW, SSR, VWL, BWV, BCV, BLT, VGF, AKF, Poly). In 10 years there will probably be 12 or 13. DVC is printing money for Disney. As more people buy in there will be more people who can book BLT, VGF, or Poly at 7 months. The MK area resorts will ALWAYS be in high demand. They aren't making anymore of them so you're looking at more demand chasing stagnant supply.
Among MK area resorts BLT has the most "reasonable" point requirement. I expect full weeks BLT to not be available at 7 months at any point of the year in 10 years. So that's why I bought BLT. I don't want to be angry I bought SSR in 2025 when there are still 30 years left on the contracts. That's a long time to stay at SSR when I would prefer BLT.