Fathers: tough love = well disciplined, well behaved. Kids who grow up without a father tend to have sex at an earlier age and get involved with drugs and generally disregard the law.
Mothers: tender love = well groomed, well mannered. Kids who grow up without a mother tend to be more sloppy, unorganized, and lazy.
Which is more important? Though this is obviously a stereotype since all parents have their differences, it is certainly reflective of today's society.