The color theory behind this is fairly intense. I have attached a document that hopefully will help explain DPI, bit depth and pixels. In a nut shell, the number of dots needed to make up one pixel is determined by the bit depth.
Remember that a one bit engine can "create" colors using individual dots of cmyk. 4 bit can create 16 shades of color. I know, confusing.
I would show the customer samples. Basically, Ricoh and Xerox are using two different ways to put the color on the page.
I hope this helps clarify any confusion.
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