We have stayed at both several times. Here are my pros/cons for each:
SSR Pros: walking distance to DS, dinner at the Turf Club Cons: Depending on where you are, buses can take awhile, huge and maze like place
OKW Pros: the studios are HUGE! we also like Olivia's restaurant, quaint atmosphere especially on the boardwalk, boat to DS; Cons: Depending on where you are, buses can take awhile; counter-service is outside on the boardwalk
Enjoy!