Game designers love tradeoffs. Tradeoffs are one kind of "interesting decision". Life is full of all kinds of tradeoffs (it has in fact been argued that life is simply a massively-multiplayer game... with extremely realistic graphics). Teaching has its fair share as well.
Here's one that I'm discovering: the more useful an experience that some exercise (an in-class presentation, homework problem or project) is, the more subjective the grading is.
It's very easy to create a multiple-choice exam where each question has exactly one, clearly correct answer. The grading is easy and the grades themselves are inherently fair. But students don't actually learn anything by taking the exam, they merely show you what they've memorized. The same is true for homework questions that are direct enough to have exactly correct answers.
By contrast, essay questions, open-ended student projects and creative exercises all lend themselves to both student and teacher interpretation. Even if you think you know what you're looking for in order to grade objectively, some students will surprise you with unexpected answers and you'll have to revise your grading methods. Sometimes a student answer will, on reflection, be better than your own. Sometimes you will simply not understand what a student is saying, and they will be completely correct and it's your own fault for misinterpreting their answer (you can weasel out of this by saying "if I didn't understand it then it was poorly written" but I would consider that the height of arrogance in most cases).
And yet, these subjectively-graded exercises are the most valuable because they force the students to actually design something.
In terms of teacher evaluations, this means that any class where I score well on "relevance to the real world" is probably also a class where I score poorly on "fairness of grading"...