Motorola Droid Razr :: Factory Data Reset With Settings Or External Keys?

The Motorola support page that tells you how to do a factory data reset gives two methods: Settings and External Keys. It also says that using the Settings method is preferable. Does anyone know why the Settings method is preferred? Is the outcome of both methods the same? The instructions (and user guide) say that the Settings method doesn't erase your external SD card, and will only erase internal storage if you choose to. Does the External Keys method work the same way? (I've used those key strokes to clear the data cache, but can't remember what the other choices are).