Steve, it depends on which driver path you're using to print your images. The following info applies to Epson K3 printers ...
... if you're printing through the RGB driver with a normal color profile (as some do for their B&W images), then the primary difference between the Perceptual and Relative Colorimetric intent for B&W images will be the tone curve. This is highly profile-dependent, in that it depends on which software was used to build the profile. In general, you'll find that Perceptual leads to a slight lightening of the print, with perhaps some better shadow detail preserved.
If you're printing through the ABW driver without a dedicated ABW profile, then it doesn't matter since Color Management should be turned off for printing anyways.