Don't Set Users Up For Failure: Use Password Guides
Sites that have password restrictions such as minimum characters, required special characters and other restrictions but do not display a guide explaining these requirements are setting users up for failure.
Don't have users take a test they didn't study for only to see the answers after they fail. The ...
As you have already stated yourself, both functionalities are complementary; it doesn't make much sense to show the strength meter without knowing what is required or entering a password without knowing whether the qualifications have been met.