Are you guys the exact same size? (who fits the frame better?)
Who has more money? (If dad, is he the kind of dad that might kick some cash in your direction and help you out on a new one?)
How much is your dad riding it?
As Scrod said, give yer dad a call.
At least you have a dad you can ride with.
I'm sure you did a great build on that bike, but no doubt you could come up with another great build if you had to.