I didn't receive any answers from anyone here (probably all busy on those Christmas pages) so I also took the initiative and contacted Epson USA myself. The got back to me the next day with my answer.

Use the Matt Black ink on matt papers and Photo Black ink on Glossy or Semi-Glossy or Luster papers. It doesn't matter if your prints are B&W or color it is the finish of paper that matters.

So in case anyone else was wondering...there you go!

Sprauncey1