This is easy. which one would make you more excited to bring to the parents. Seriously.
And if that doesnt work. Tell your mom that your brining each one of them home for dinner ( on different nights of course ). Then tell the girls youd like to have dinner at home and see how they react. Maybe one of them isn't really looking for something and that's an easy way to find out.
No parents, suggest double date.
Still no answer, let your mom pick. Then you have leverage on her later on.