It's all about control
In each writing technology and in each text, the question is: how and to what extend does the writer control the reader's experience of reading?
Bolter in WM, pg 77
I really never thought of the how much control the writer actually has over the reader. I've always thought that the reader gets as much out of the text as he puts into it, but this makes sense. The amount of detail in a text dictates how much a reader can experience while reading. For example, an essay is going to have a lot less sensory details than a short story might.
But what about oral writings? Are they more experiencing because you have to pay attention more actively and rely on your imagination. Some printed or manuscript texts might have pictures to go along with the written texts.
We cannot say how Homer's original audience exercised that control: they may have shouted advice, or they may simply have shown greater or less interest as the performer proceeded.
I guess this is just another way to look at viewing a play versus reading a play. The author has a different amount of control of the audience in each situation. It might be easier for the audience to understand what's going on in a play if they see it with their own eyes, but if the audience takes the time to read the text, they might also learn a lot about stuff that was overlooked during the physical production.