Both resorts will have 2 bedrooms with a wheelchair accessible roll-in shower.
I've never stayed in a handicapped room at SSR, but did stay with my Mom in a wheelchair accessible 1 bedroom at OKW (a 1 bedroom will have the same layout as the living room, kitchen and master in a 2 bedroom). She loved how easy it was to move around the room due to the large size. SSR's plus is being able to independently go to Disney Springs without needing to wait for an available wheelchair space on Disney transportation.
SSR will be a bit easier to book, since some people book the OKW wheelchair accessible rooms to guarantee they'll be on the ground floor (most OKW buildings do not have elevators unlike SSR), but neither should be too difficult provided you're looking to rent on non-popuar dates or greater than 11 months out.