for gauchuas and all the dwarf species. the male's head is bigger than the female's of the same size. the male's head bulges out more where the jaw line ends. (cheek)
and from what i knoe... its very hard to determine the sex for larger specimens of SH.
juss looking at my gauchuas, the male flares out his fins and inflate his head when others come by. he does that to every SH except he attacks everyone but his mate. he will flare out his gill and inflate his head but stops once he recognizes that it's his mate.
also my mail seems to be very dark in color compared to others.
for me it was easy to determine the sex because the male is the biggest,darkest, most active one in the tank and my female is very light, the white color from his belly comes up to the eye in the cheek area and she has a 1 large white scale? (i dunno why) on top of her head. (like the gems that females in India places on their forehead to symbolize that they are married? or virgins..... correct me if im wrong)
this is from my experience and as soon as i see them mate i can confirm it.
but other than that i am 100% sure that the male has a larger head than the female for the dwarf SH.