In the communications business, it's almost impossible to use one or the other. For high end graphics, Mac is the standard. In fact, there is often a problem using, for instance, Quark for PC with a printers image setter, or when going direct to plate or press. For statistics, analytical software is usually more abundant and easier to use on a PC.
Left brainers (linear thinkers)seem to have an easier time with PC's, and "big picture" right brainers are more comfortable with a Mac.
For our business, at least for the near future, we'll be using both.
Russ