this is another one of those "depends on the school" type question. Generally, i think its fair to think there's a direct relationship between the length and number of essays and the importance in the application. Duke, Northwestern, and other schools with multiple essays on various topics or one/few long essays (I'm guessing loyola falls in here too), i can only imagine the essays you write are very important. At USUHS, my interviewers gushed over my essays and it was clear that making sure i could articulate an interest in military medicine was key to them. If its GW, Temple, or other schools where its just a 4 line blurb about why you want to come here, i just put in the obligatory stuff about location and whatever. Point being, if its clear they want a well developed essay, put some substantial effort into it.
and schools like BU (give us your 100$ and a pic), well those essays cant count for much if they dont exist 🙂