This varies from individual to individual (I don't mean the preferences, I mean the individual being looked at). I've seen some guys that are more aesthetically pleasing than some girls, and vis versa. Plus, in terms of reality, I don't see it as a strict dichotomy where men = muscle and women = curves.
The male body of course. We are mammals after all. Is there anythin about the female of the species that isn't related to producing and nurtring babies? No there isn't. Would you ever say a lioness is better looking than the lion. No, you won't.
There's no difference in how bodies function (Excluded veginas and breasts), both have muscels that works the same, it's only how where the fat gathers. For male, fat gathers mostly around the waist and belly area while woman's fat gathers are more or less spread out all over their bodies, primarly around their thighs, however it's this even spread of fat that gives women their nicer curves (If they have an okey weight that is).