I may not be much of a difference, but I'm sure families with a son and a daughter both playing would prefer they not have to pick a child or divide and conquerI know it makes for a long night if you are a fan. I can see where the girls wouldn't like it when 90% of the crowd is there to see the boys.
I am often asked why OCC boys and girls play on the same night at opposite venues. I don't think it has any affect on attendance in the OCC. In smaller towns it would definitely affect attendance as you have support for the school no matter who is playing.
In my experience the girls teams have loved it. Brings a bigger crowd for them and the boys team may not regularly attend their other games so it gives them a chance to play in front of more of their peers.The girls don't like it. They feel like they are the JV game for the boys.