One thing about black mattes is, they can look really flat and downright silly in a bright, evenly lighted environment which will turn the black into a weary shade of gray and reveal even the tiniest speck of dust on the glazing. You gotta think about where the picture will be placed, and relatively few places will work for black mattes. And don't forget black mattes exaggerate glazing reflections.
Saw a show where every piece was surrounded by wood liners hand wrapped in single pieces of black velvet, no seams. 1/2" deep bevels on the liners. Dark room, each print spotlighted. Totally dazzling effect, as though the prints were surrounded by complete darkness and glowing from within. But anybody who bought one of those things and put it up on their typical murky living room wall would be very disappointed unless they duplicated the lighting situation at home, starting with turning their living room into a black pit. And BTW this only works for prints with killer max-D's.