Philosopher, the problem with celebrating boys bar mitzvahs much more lavishly than girls is it makes many girls feel like second class citizens. At a time when girls are reaching an age of becoming who they are (as are boys), its hard to see fact from fiction.
Why does a bar mitzvah boy need a nice hall and a girl gets a meal in her house? Why does the boy get to invite all his friends and family and the girl doesn’t? Why does it feel like Judaism is all about men and women have to stay at home?
Teenage girls are searching for meaning in life and making a lavish affair for your sons and not for your daughters will send them the message they aren’t important. I’ve spoken to enough struggling teenage girls to know this is true.
When I make Bar Mitzvahs (I have no daughters yet so I don’t know what I would do with them), I want to concetrate on the shul setting and the mitzvah. Not on the party. I want to send the right message to my sons that its the mitzvah they should be celebrating not the party.