Being the cosmopolitan worldy man that I am, both cities are fantastic. As a life long midwesterner, I can tell you what it is like from outside looking in.
San Francisco is much easier for the outsider. To get along in New York, you have to think like a New Yorker, aggressiveness and assertiviness abound. Not a place for the thin skinned. In San Francisco, anyone can have a phenomenal time as long as they are tolerant and open minded.
Conservative businsessmen on the cable car next to leathered hard core gay couple making out without anyone giving a shiit has been seen by moi. NYC probably okay with that but definitly on a faster pace. In Cincinnati, thats a felony 4, minimal 2 - 5.
NYC and SF both liberal towns, fast moving, very alive cities. A person can live and breath in both. SF safer in general.
Eddie