I write fantasy because I love fantasy.
I like literary fiction but I don't write it.
One reason is that I'm not sure I'm equal to the task of putting characters convincingly into modern life. They say that writers are great observers of people, and that's how they bring you the world through the eyes of a young girl, a teenage boy, a twenty-something socialite and professional working woman in an advertising agency in London, a fifty-something council-worker in a failing marriage in Birmingham, etc etc. How do young women in offices chat to each other? What conversations do old men in nursing homes share? It has to feel authentic because these are things many readers may have experience of, or at least an impression/opinion on.
I'm more of a great imaginer of people than a great observer. That makes me better suited to fantasy where the opportunities for a reader to think 'that's not right' are fewer and further between. I feel I can portray people and I can project them into unconventional settings in ways in which the reader is prepared to accept.
Which brings me to the latest book I've written. Red Sister. It's the first book I've written from a female point-of-view. If you discount Katherine's journal entries in King of Thorns and Chella's brief chapters in Emperor of Thorns, then it's the first female point-of-view character I've written. By which I mean (for the non-writer) a character whose eyes we view the world through, not merely a female character seen in a book.
Red Sister is a story delivered entirely (99%) through the eyes of a girl, and much of her time is spent at a convent surrounded, naturally enough, by other novices and nuns.
I normally only have one beta reader, but for Red Sister I've asked several people to read it. Most of them happened to be women. I'd asked them for feedback about whether they enjoyed the book - what worked, what didn't. But today (for the purposes of this blog) I asked those readers whether they thought the scenes with the main character and her friends were convincingly written?
They said, yes.
So then I asked - because I had made no conscious effort to make the characters female - whether it was the writing or the setting that had made that portrayal successful? I asked, if I changed every she to a he, every convent to monastery, every abbess to abbot ... would it now ring false? Would my boy characters now seem 'girly'?
There was some talk about girls and women being 'more about relationships' and 'interpreting more levels in a conversation' but at the end of the answer was 'no' - if I swapped everything around my convincing girls would be convincing boys.
And that fits with how I wrote the characters. I don't know if there are fundamental gender differences or how to portray them if there are. So I tried to write convincing people - put them in a setting, and had them react appropriately to it and the situations arising. I basically ignored gender and wrote people.
One of the beta readers answering my queries mentioned Robert Jordan - who I have not read - and said she thought he wrote women poorly (though in good books presumably as she seemed to have read a lot of them). She felt he was always conscious when writing women that he was writing women and dug into his collection of "female traits" to let us know what we were dealing with. She noted that his simpering young novice and centuries old powerful witch were essentially the same, both the stereotypical female portrayal of a previous generation - over emotional, weeping over imagined slights. I wondered if I might have a similar problem but in the opposite direction - that my young novice and seasoned woman in authority might both be the no-nonsense unflappable confident type we expect the latter to be. She thought I did manage to differentiate though.

It's not (I hope) that I'm writing women as 'men with breasts' - more that I'm writing characters / people, and both genders can be thought of as 'people with [add gender specific organ]'.
In any event. The TL:DR version is - I don't know how to write women, so I write people instead. The person's role and situation may depend on their gender (depending on the society they're in) but the person themself is just a human and that's all I try to depict.