Both OKW and SSR are "park-at-your-door" apartment complex style resorts. Both are lovely, and both have a rather spread-out, relaxed ambiance. Both are quite near Downtown Disney, with SSR being within easy walking distance of DTD Marketplace (the East side of DTD). Both share boat service to DTD, again with SSR being closer.
If you have a car, in many ways either resort is convenient, depending on where you are going. From OKW, I'd bet I can beat a BCV'er to anywhere in Epcot except maybe France or England. And I know for a fact that I can beat them to MK or AK. They'll probably beat me to MGM, but not by much.
I don't claim to be a bus expert, but the busses you rarely hear complaints about are OKW. You do hear complaints about SSR, BCV, and BWV busses. You just have to read and evaluate each of those complaints on their own merits. I personally tend to agree with Doug's comment, "Heck, I'm on vacation so what do I care if I sit at a bus stop for a few extra minutes?"
BCV, BWV and VWL are attached to luxury hotels, and enjoy the hotel amenities. [ETA: BCV and BWV are in between Epcot and MGM, and if that's where you are going, great! If not, OKW or SSR might be more convenient.]
YOUR decision is basically not what you WANT, but what you can GET. You'll be fine with either OKW or SSR. We took Grandma and Great Aunt to OKW last Dec 4-9, and they were totally blown away. We just got back from 5 nights at OKW, and loved every minute of it. I'd personally probably go with OKW because a) it's finished, not under construction, b) Olivia's, and c) if you have a car, it's a little closer to where you want to go.