The people in Buffalo seem to be a bit nicer/welcoming than Rochester. Maybe it's the "no airs" (no illusions of grandeur) blue collar mentality vs. Rochester historically being more white collar (Kodak, Xerox, Bausch & Lomb were all based here, and one can't forget Wegmans!).
That isn't to say Rochesterians aren't friendly.
But Buffalonians are some of the nicest Americans around so
I like Rochester, they have pretty residential streets with nice landscaping, parks, the Genesee river falls right in the heart of the city, but Buffalo has a bit larger of a city feel and downtown/urban core doesn't feel separated (disjointed?) like Rochester.
Buffalo has a larger feel since the population topped out in 1950 at 580k people in a tiny 39 sq miles, and the Metro pop. peaked early in 1970. Also Buffalo has a (c. 1985) light rail line that functions like a subway, and of course major league sports.
Visit them both and see what you think