I stayed at Old Key West for the past 5 years as my mom owned there.
I just had my first visit at SSR ( I just bought in) and what a difference.
My BIGGEST complaint about OKW is the resort layout. Yes, SSR has more rooms, but OKW is more spread out. If you are near the end of OKW, to walk to the main area/pools can easily take 15mins or so. To wait for a bus can be just as long if not longer.
SSR from end to end is about 5mins or so.
I did not notice a major room size difference, but folks SAY OKW is bigger. I just stayed in a 1bed and didnt notice.
Other than the resort layout, I would say they are completely comprable.
I do prefer SSR though.