OKW is a very large resort. From the closest point to Downtown Disney, it's a little over a mile walk to DD.
Geographically, OKW and SSR are right next to each other. The walk from the CLOSEST of the SSR buildings will be shorter than from any point at OKW. But buildings 5-12 at SSR are quite a distance from the water, and would thus be a longer walk.
OKW currently hosts a pontoon boat that seats about 12, which runs to and from DD about every 20 minutes. Closer to the SSR opening, a larger boat will be placed into service which will make a round trip between SSR, OKW and DD.
All-in-all, OKW and SSR are going to be fairily similar resorts. OKW is only available via resale, which means you can get it quite a bit cheaper than buying SSR direct from
DVC. But, one of the main selling points for SSR is the additional 12 years on the contract.
Examine all of the factors and decide which route is best for you.