I think you could look at the OP question in two different ways.
1. What is the best inkjet printer for producing neutral B&W images, using the manufacturers stock ink/profile/drivers? Or basically, printing right out of the box.
2. Or what is the best inkjet printer that may be used (and/or converted) to produce neutral B&W images?
If I were trying to print only B&W images, I would definitely be leaning heavily towards a wide format inkjet printer, converted as a dedicated B&W printer. I converted a new 9890 to K7 piezography for both glossy and matte B&W prints. But I think in retrospect, a 7880 or 9880 may be a better choice for MPS gloss. Fantastic B&W images.