Help with subcategories

[printerresearch.com]

Hello, I am Robert Littlejohn the web developer for Printer Research
I am trying to develop sub categories for the professional photo printers section of my website. I need to know how a professional studio or high end amateur would go about researching their needs in a photo printer, what would be the first thing to look at. Some have said types and quantity of ink, some have said width of print, some have said resolution is the main factor.

Any posts to let me have a clear picture of how to design the sub categories would be appreciated.

Thanks

Robert Littlejohn
http://www.printerresearch.com