I don't know what I'm having (and we don't care). I've been told, by various different people, that boys are; more loving, clingier, more likely to cry when hurt, easier, dirtier, likely to speak later, likely to walk later, likely to walk sooner, more likely to successfully breastfeed, and need fewer clothes.
On both sides of our family the firstborn was a 'good' baby, slept through the night, fed well, could be passed around, slept wherever, and the second born was a 'demon child', screamed and screamed and fussed and was a nightmare. My family was Girl then Boy, OH's family was the other way around.
I refuse to believe that your genitals impact your behaviour as a baby (I also refuse to believe that the babies genitals impact the shape of my bump, how sick I am, or any of that other pregnancy stuff either).
I do think that if you go in with certain expectations you're more likely to get certain results. If you tell your girl off for playing in the mud but not your boy, because she'll ruin her princess dress, then you get what you expected.