Well, in the wild the female is the dominant sex. So they might have a tendency to be a bit more nasty to each other.
But I don't think you'll find any difference in their behavior, or anything else, when you get one or two pet chinchillas.
Their personallity depends on how their parents are. So if you've got an aggressiv mother or farther, you'll probably get an aggressive baby. If the parents are nervouse, the baby will be nervouse and so on...
I've only had 3 males and some male kids, but they seem to be a bit more friendly. Our 5 girls are a bit more reserved than our boys.
But all in all they all behave more or less the same, if you don't know them