I believe that the subjective is better for testing of a thorough understanding of the material. The best combination, though, in my mind, is to mix the two so that the subjective responses require objective information, as well. I find the subjective evaluation easier to acquire an understanding of just how much a student knows because there is no guesswork involved. In objective, the student who doesn't know the answer to a question can always guess and sometimes (if not often) guess correctly. That gives an inflated result. This student would not fare well on a subjective exam, particularly if specific data is also required within the essay. The problem in grading the subjective in my area of expertise is the student who might come up with a valid interpretation of the material that is different from mine or other sources. That makes it extremely important that I remain open-minded and don't start forming an opinion of the answer until the answer is complete. Even then, I have to be careful about the validity of his/her answer. With essay exams of that nature, I re-read the essay one or two times later to check on my own biases.