When dithering one can put down the dots in a regular pattern, this can result in a rather unpleasant effect of some lines being one color and the same type lines at a different location being another color. Diffused is recommended, but it also has problems especially with lower resolution printers. This is because the manufacture's inks very from company to company. Epson's cyan may not be Cannon's cyan. Finally, it does no good to print using a 1440 dpi printer, if the paper you are using is only good for 300 dpi inch.
Poor resolution imply poor reproduction of lines and small symbols.