I've been in Sept and some days can be very hot. I'd prefer to be at BCV for SAB and close proximity to Epcot and MGM would make bopping to/from the resort very easy. Especially if you want to grab an impromptu meal. (We wouldn't necessarily leave SSR, OKW, or VWL just for dinner at a park. Travel times and hassle can be huge.)
Think fun in the park in am, easy swim when it gets hot, lunch at beaches & cream (no way Jose sundae!), lazy river, meander to park for dinner, meander back for R&R or sweet treat at the Boardwalk.
BWV would be great too. But, SAB is a big advantage.