Most teachers would have a rubric for the speeches that students have to give. That rubric would determine which of these students would get the best grade. The rubric would tell us things like whether a longer speech is better than a shorter speech. It would tell us how important it was for the student to avoid words that the audience would not know. Most importantly (in comparing A and X) for example, it would say how important the content of the speech was when compared to the delivery of the speech.
From the way you lay this out, it is clear that you think that Student A should get the best grade. I can't really say what should have been because I would want to judge for myself the amount of expression the students had or how well they engaged the audience. Not seeing it for myself, and not knowing the exact weighting of various factors on the rubric, I really can't say who should get the best grade.
For example, a rubric that values using the right vocabulary, coming in at the middle of the time range, and speaking clearly without pausing or stuttering might give S the best grade. One that was mainly focused on the academic content of the speech would favor A. It's just not possible to know for sure.