Both mean the same thing. The difference is how they combine with other words.
According to this, is more about individuals while is more about the ministers as a group of people.
My impression is that they are not so interchangeable.
* _Minister of Foreign Affairs_. Not
* _will become a PhD or a minister in future_ \- an oldish set phrase to describe a promising child (although I don't see much future for Japanese PhD's and ministers now). is not possible.
* _Prime minister told ministers in charge to take necessary actions_. is not possible.
* _A person who was a minister in the past_. To me sounds OK, but it is much less common.