How to explain it...? When I say "Slender, I really mean the HEIGHT of a fishes body in profile. Male bodies tend to be taller, causing their heads to be larger etc, them a female, whose form seems more streamlined and pleasing to me.
Domesticated bettas for years have been bred for finnage and color...but I feel that they have lost a great deal in the shape of their bodies. Perhaps it was since the original domestics were bred to be fighters, so they bred for larger jaws...? I'm not sure...but the grace of a wild betta's longer body is certainly appealing, and I wish to see more of it in the modern domestic betta. I think we can all learn from the original betta form.^^