What benefit for admissions is it if a parent is faculty and received their degrees from USC?

I think faculty children have an advantage even more than legacy.

It depends on how powerful your parent is. I live in a town where a fair number of kids are faculty children. Many get into their parent’s employers without necessarily having the stats. It won’t make up for a B average, but an A- student can often get into an A school. Schools take care of their own.