Well honestly, you find out which is warn and you replace it or the bushings. If one is real bad the other has at least the bushings gone so replacing them too is of course recommended.
What you do is open the door and have someone lift up on the door from over at the latch area (the end of the door) simply squat down and lift the door up. While this is being done look close at the hinges and see where the movement is coming from, you will quickly see what is worn.
If you are going to replace them come back and see us, there are a few tricks.