I have had HP and Epson, and HP is much less of an ink user and waster.
HP even has a printing chart of how much ink the printer will use with your paper on different types of coverage. From my expereince, you can also leafve the printer on without printer for weeks, and come back to a perfect print.
If this is true to the Z or other HP's, I think this is enough reason for me to go with HP for my future printer. For now I have an HP 130 Designjet 24", and I have a clog in one of the heads, but if I can clear it I will continue with it, since I have had it for 6 years. It has problems for sure. The tray doesn't feed paper(even when new it had issues). Other than that the EFI RIP is to blame for not supporting 1200dpi on some of the best papers, like Proofing Gloss, and another I cant remember. This was a big issue for me, as I purchased over $2k worth of media when I got the printer, then to find out I can't usse the EFI ICC with it.
For me, I would go with HP, then Canon, then Epson. But I do hear Canon needs to run regularly. I wish they could be more clear about these usage issues. Epson will do an automatic cleaning from time to time to keep things primed, and ready, but is also rather thirsty with inks.
Maybe for Canon and HP, if you have it connected and ON almost constant, there can be a program to auto print off a small swatch from all the inks to keep it from clogging?