It's not all about size despite when men think. It's more about shape and overall quality. In this case if I were to choose one as a mate for Big Boy, I would choose the fish in the first pic. I know that she (I think that she has a better chance of being female due to her underline) doesn't have the color of the other (which I feel is male) but she doesn't have a bump on her head. Finding the perfect mate for an excellent fish is so hard. I know from experience.