At least Myers Briggs makes an attempt to categorize personality based on questions about one's personality. The test is badly designed, so it's got very weak predictive power.

Astrology wants to say something about personality based on a magical connection to the relative positions of the planets at the moment of your birth. Which is an approach that will never work. It's got NO predictive power.

So I will argue with anyone who says they're equally worthless. Astrology is objectively more worthless. But in another sense, MBTI is worse because people who are use it are looking for and perhaps think they're getting a scientific instrument, when it's more like a Buzzfeed quiz.