The 3 color ribbons combine three primary colors to create black while the 4 color ribbons come with a separate black. I expected to see muddy blacks from the 3 color ribbons but after much fiddling around and effort I could tell almost no difference in the black output from the two ribbon types. I switched back and forth several times trying my best to get muddy blacks but they just didn't happen. Personally, I can't see any reason to pay extra for the 4 color ribbons. Spot colors look brilliant, sharp and clear.
Process colors are where the mud comes in.
I couldn't get my gradient fills to look as nice as I would like them to. Some of my greens just didn't look very green. I couldn't get a brownish red that I was trying for. The Tektronix did a better job although some banding was evident from both printers. I reloaded my favorite version of the drawing, switched to dye sublimation, hit print and left the room for awhile.