What are the principal differences between face-to-face and virtual presentations?
There's quite a difference between these two kinds of presentations, as anyone who has sat through both can tell you. These are the principal differences that come to mind (although it sounds like perhaps they are looking for a specific textbook answer?):
1) Virtual presentations - over the internet or with video, are two dimensional, subject to the proper functioning of technology (always a dicey proposition), and, since they are less personal, they are easier to ignore/not pay attention to.
2) Face-to-Face presentations involve body language, greetings, rapport and personal interaction. They are, however, much less convenient to deliver and are subject to limitations in the distance you would need to travel, and the need to give presentations repeatedly instead of perhaps only once.