We own at SSR and BCV...like the other posters, we find walking to Epcot and the Studios "irresistible." We also just love BCV and BCI "for themselves." While we like SAB a lot, we mostly use the BCV pool (a sort of "quiet pool")...I like to swim for exercise, which is virtually impossible to do at SAB...we do use SAB and enjoy it, but use the BCV pool considerably more...
But we also really love SSR...the main pool there is, like SAB, not so good for "exercise swimming," but it's a neat pool...we like it a lot...and we really like that it's "right at" Artist's Palette...we also love the Grandstand feature pool and young ones really love the interactive water play area there. I'm also a walker...and walking the grounds at SSR is a treat...
Of course, there's the spa and the golf at SSR for those who are in to those activities (not so much for us)...
But there's one huge advantage to SSR that many people seem to overlook: if you're at all in to resort hopping, or dining at one of the resort (as opposed to park) restaurants, SSR's proximity to Downtown Disney makes using Disney transportation to the other resorts MUCH easier than it is from other resorts...if you get a room in Congress Park, it's a 5-10 minute walk (depending on what end of CP you're at, and how fast you walk) to a bus that will take you directly to your resort/restaurant...every other resort you have to do some kind of transportation transfer...this is a huge advantage after a late-ish dinner when the only Disney transportation running is to and from Downtown Disney!
We also don't consider a trip to Disney complete w/out a visit to Downtown Disney...and Downtown Disney seems to be the most "difficult" of the Disney venues to access from the resorts...in 16 years of regular trips to WDW, we've always found the DTD buses come the least frequently (especially prior to evening hours)... SSR offers the easiest access to DTD--
Plus, if you need a "real store" (something not carried in one of the resort stores), you can easily (about a 20-minute walk, or a $5 cab ride) access a drugstore (and I think a grocery) right near Downtown Disney...not a huge factor, but one that we found most beneficial on one trip recently when we had to have an "emergency" prescription filled...
So...as w/all the Disney resorts, there are advantages to each...I'm happy as can be w/my ownership at both SSR and BCV...we've now stayed at all DVCs except WLV and BLT and while there are times when availability is an issue, we have by no means found we "never" get to book other places...we also frequently decide "at the last minute" to do a trip (a byproduct of having a college student for whom "planning" is a disease!) and we've never been unable to book somewhere, or been forced to book w/cash...and that includes two spring break trips planned less than 2 months (and in one case, less than 3 weeks) prior to arrival...
So, for us, if we were buying in for the first time now, we'd find the economics of SSR irresistibly appealing...you can always add on at BCV (or another resort) later if you want an 11-month advantage for particular trips...(that's how we acquired our BCV points)...
Good luck w/your decision...