Neither of these machines is designed for heavy use. Lexmark rates its unit for only 3,000 pages a month. Though that might not satisfy the demands of many businesses, it's a lot for most home offices and even some small businesses that do a minimal amount of printing and copying. It could also be suitable for busier offices as an extra copier or printer, perhaps dedicated to one or two people or used only when the heavy-duty machines are busy. I find myself using my personal copier for small jobs and using a copy shop for larger jobs.
Color is considerably more expensive.
Both devices can be connected to a PC via either a parallel cable or a USB cable. As a copier, both machines work like a regular stand-alone flatbed copier. The Lexmark Z82 makes good color copies, but the color copies from the Hewlett-Packard G55xi are even better. I copied some color photos on HP photo paper and it was almost impossible to distinguish from the original. Even when I enlarged it to twice its size, it still looked fine and produced a reasonably good-quality copy on plain paper.