Tom-
I was told not to run both Postscript and raster driver on the same machine when I first got my printer, but have since been told that this is no longer the case. As a matter of fact, I have both on my computer and am able to pick which one (primarily the raster these days, until they issue an update for the Postscript version) as needed. The print window that runs downstream of Photoshop is similar, but annoyingly different in the two versions. The differences are stylistic, not functional, and seem to be the result of giving two teams the task of designing the two interfaces without coordinating between them. Once you get used to it, I think you will find the raster driver slightly easier to use, with a couple of less clicks per print to send a file to the printer.
-Ron H.