I can only speak for me. I’ve known from an early age that I ‘liked’ both sexes. As I got older, found out it was true...I like women more, but men are good too. I don’t meet many other bis of either sex, so I don’t know if more are women.

Who knows? And more to the point, why does it matter?

No way to know without polling everyone on the planet, and being able to assure they're giving honest responses ...

I don't like to just make guesses on things like this. I am sure you could find some studies related to that

I don't know. It seems that way, but probably just because women don't seem to have to deal with the same hard core taboos about being close to the same sex, at least in the past, though that may be changing now.