Can one grade with equality when the presentations are so varied?

Honestly, this question did not even cross my mind. But now that you mention it, I guess there is a lot of ambiguity in how this multimodal project could be presented. The wide range of possible products could potentially make it difficult for a single person to grade. Generally, projects are restricted to a particular medium, such as a paper document. This makes it easier to compare the writings of each student. Instead of having to compare every single aspect of the project, you only need to compare certain components since the medium is kept consistent. When the medium is left up to the discretion of the student, this makes the grading process more difficult. 

I am obviously not a teacher, but I would guess that there are multiple ways to go about grading assignments in order to maintain an unbiased mindset. I'm guessing a common way to go about doing this includes determining which person's project is optimal and deserving of the most points. From there, you can base each of the other student's work on the standard set by the best project. When comparing papers, this would be much easier because the grader could actually point out errors that were made in excess to the standard, which was set by the best paper. However, when the mediums are entirely different, it makes it much more difficult to determine which project represents the standard. That standard is set based on the prompt and what the teacher has in mind.

For example, my project is compiled into a short film while another student's is a presentation on Prezi. One must wonder, what criteria are used to decide what grade is given. Does the teacher take into account the difficulty that comes with certain visual mediums? Or does he solely evaluate the information and the argument that is presented using that visual? Will the grader be impressed by a more complex production, or will that not break his unbiased perspective? I wonder...