Some things to consider:
Contract Length - Not sure if it matters to you, but most contracts via resale for OKW have a 2042 expiration date. SSR expires in 2054. If you purchase OKW through Disney, you'll get the 2057 expiration, but will pay a lot more per point. As for SSR, if you have the patience, I would never purchase it through Dis. You'll get a contract for around $79 per point, and last I heard, Dis was selling both OKW and SSR for $104 per point.
Layout - I've stayed at both and love both. I prefer the decor of SSR, but love the space, balcony and landscaping at OKW. Both are spread out, so if you get assigned a room far from the main building, it's going to be a haul at either resort. At OKW, you can actually reserve near Hospitality House, which will guarantee you certain buildings. At SSR, it is only a request (Congress Park, the Springs, Grandstand).
Point Structure - The point structure at OKW is more reasonable, so your points will go further. For example, I was just out playing with the points calculator for a trip this summer. A 2-BR at SSR for 5 nights (Sun arrival, Friday departure) is 180 points. A 2-BR at OKW is 150. A 1-BR at BCV is 150. So, point per point, your points will go further at OKW.
Maintenance Fees - The maintenance fees are close. There's not enough of a difference to sway me either way
(SSR = $4.21 per point versus OKW = $4.56 per point).
Unit Size - If you ever think you'll reserve grand villas on a regular basis, I would purchase at OKW. It will cost you 501 points to book a GV in the summer (Magic Season) at OKW, or 719 for the same week at SSR.
At the end of the day, the resorts are similar, and it's a personal preference. It was easy for us, because we cared about the contract length, and OKW (at the time) expired in 2042. If I were purchasing today, it would be tough for me, as I love OKW. It would be easier for DH and DS (13). They both prefer SSR. DD is too young to have an opinion...she's only 6!
Best of luck deciding.

They are both beautiful resorts, and you will be proud to call either home!