Digital BW, The Print

I use the HP Z3100 daily and it does the best job with black and white imaging that I've ever used, EXCEPT for a dedicated monochrome inkset. Personally I use Cone K7 neutral and carbon sepia and the quad sets are great too. It is not possible to achieve this level of subtlety with one black and two grays. Though there are prints that you can't tell the difference on, many you can. And if you shoot 4x5 like I do and have the values to print you can do it.  I'm sure the MIS pigments of 4 or more dilutions are more subtle also,  just haven't used them. Since  Paul took that over they became much more feasible. 

 Also, as Walker pointed out, the Piezography K7 has higher resolution potential and clog free base. 

Now the Z3100 Vivera pigments have a better dmax, of 1.8 on Photorag vs 1.67 K7, AND unlike Epson you have neutralish grays on photo papers ( selenium tone on photorag )  so you can to a tritone with NO color channels involved at all. And, you can print on the new baryta papers successfully. In that way hue consistency throughout the scale on all papers is a no brainer. If HP had put one more gray in that 12 ink set up they could have kicked ass. They chose to include a green and blue instead for some odd reason. Maybe if they come out with an update to the Z3200 in a few years they will consider that. They don't need the green but they do need another light gray in my opinion.

John