To me, a blanca (cypress back and sides), a negra, and a classical guitar are generally distinct.
The soundboards of traditional flamenco guitars, as opposed to classical guitars, are either thinner, or braced more lightly--or both--which gives the sound of flamenco guitars more of a rough, raw, raspy character. Often the backs and sides of flamenco guitars are also thinner, though not in the case of mine. I use spruce almost exclusively for soundboards.
Although I am afraid that talking about sound quality may be like dancing about architecture, I think a proper flamenca blanca has low sustain and what used to be called a "tinny" tone--less full and round, more fundamental, I suppose, and somewhat rough around the edges. The sound of an Indian rosewood negra is close to that of a blanca, but with more depth. I find that other rosewoods, such as Bolivian (Santos) or Brazilian, give a mellower, more refined sound, as does hard maple.
Classical guitars have more sustain and projection--more like a piano, perhaps. My classical guitars sound totally different from my flamenco guitars. And I keep the same body depth and plantilla for all my guitars. Currently the differences between my classicals and flamencos are the soundboard bracing--including the biggest brace, the bridge (and thus neck angle); the scale lengths (650 mm for classicals and 656 for flamencos, generally); and that I use a mahogany heel block for classicals, which I find adds sustain to an otherwise cedro neck.