Are U.S. "college rankings" or "subject rankings" more important?

What is more important, overall university ranking or university ranking by subject?

Since US colleges follow a liberal arts curriculum, college ranking would be more important. However if you’re already very clear about what you want to study specifically you might care more about ranking by subject, e.g. Berkley engineering is very famous (has the same acceptance rate as some ivies), so you might choose that over ivies that have weak engineering programs.