An odd thread but one I think some folks can get some useful information from:
HP Designjet 5500: Older aqueous printers that are mainly used for trade show graphics as bigfish said.
High cost per square foot in ink and media. Easy to use and suitable for an office environment with no fumes. Indoor durability good. Outdoor durability is poor with no water resistance and rapid fade issues. Aqueous printers usually sit without use for months with little ill effects to the printheads or parts.
Roland printers are the workhorses of our industry with excellent long term outdoor durability, low ink and media costs. They do however introduce solvent fumes into the printing environment and are not usually used in typical office situations. Also slightly more maintenance than an HP 5500.
Solvent printers do not sit well for long periods. They will dry up without occasional printing and maintenance.
HP L25500 (Latex) is a new technology that does a good job of giving the ease of use (operation is virtually the same as HP Z6100) and no solvent fumes while still having long term outdoor durability. The ink is slightly cheaper than solvent and it uses the same media as solvent machines. From my limited exposure to this machine it seems like it can sit well for long periods with no maintenace like aqueous printers.
Choosing a printer is a big decision. Good luck!
Take a trip to Orlando FL to the International
Sign Association Expo in April. It will be a massive education for you and will make your decisions much clearer.