The Brady plotter uses head technology developed by Fuji, and the latter three use the Seiko Epson 64 nozzle piezo heads, which are used in office printers as well. Large-format phase change plotters now on the market are available from LaserMaster, Tektronix and Mutoh. The LaserMaster DisplayMaker Express uses head technology from Spectra, and the latter two use heads developed by Tektronix. As mentioned above, one key advantage of piezo heads is their ability to work with many ink types, including pigmented. It's important to note, however, that pigmented inks are now available for thermal inkjets, so even without making the move to piezo, inkjetters can take advantage of pigmented inks.
Pigmented inks are desirable because they stand up to UV light much better than dye-based inks.
Second, the pigment molecules fall together in a lattice of crystals. When hit with UV raditiation, this lattice flexes to absorb some of the energy of the radiation, leaving less to destroy the molecules. This means there is less dot gain with pigmented inks, a fact that users must consider when selecting their media and deciding how much ink to apply. Because the pigment particles tend to glom together, sinking to the bottom of the solution and clogging the head. Also, the big particles tended to scatter too much light, giving finished prints a muddy appearance.