Everything in my life has led to me believe they are very similar, and it is society that causes such huge differences. Of course, women and men have different genitalia, and men are natrually physically stronger than women (or more able to be).
But aside from that, there is little difference. There are assertive men and assertive women, sensitive men and sensitive women etcetcetc. The mass media publicises ideas of men as sporty, career-driven and into sex, beer, football, and women as obsessed with fashion, beauty and relationships.
I mean, how are blue and pink actually signifiers of gender? They mean nothing but what tradition has decided, and nor, I think, do the other qualities society gives men and women.
Just my two cents…
It is difficult to see what we would be like without the influence of societies. We have had somewhat different roles because of biological differences. The sex of a person is becoming less important than their mental abilities. I think it would be boring if we were all of the same sex. And there were were no differences. We are all human beings we are more alike than different.