...Dell would have me think so, but I can't quite believe it. Can anyone explain to me the difference between the minitower drive and the desktop drive ? Or am I correct in thinking it's purely a marketing difference?
Since the part numbers differ, I would not assume those are the same device. They appear to be compatible, and of roughly the same capabilities.
It's possible, and somewhat likely, that Dell markets these drives for certain models so they can provide a bezel that matches the case of those systems. Adding one of them to a computer they aren't meant for may work, but they may not fit quite right in the case.