Epson 10000. Six channel head, three wipers running across so not over the total length, each wiping the nozzles of two channels and nowhere wiping a channel color over another channel color. In the x900 models one wiper runs over the entire 10 channel nozzles surface.
On the pressurising system; the 10000 had just behind the cartridge slots 6 electric valves on the ink channels, by that there was no need for the backflow blocking valves in the carts but they were still used (not on hacked carts :-) probably just to discourage refilling. I wonder if the electric valves are still present in the models after the 10000. I do no think a cartridge backflow blocking valve is entirely tight in time for a water column of say 20 cm pressure. When on power a leaking air membrane in one of the carts could give a low pressure error, how fine tuned that was I do not know. The last is still used on the x900 models, I believe the 11880 has three air pumps, the x900 might have too.
The ink buffers and dampers system was integrated in the 10000 head, both probably bigger than in the models before and after it that separate the dampers from the heads. At one hand you could not replace dampers but on the other hand they were aimed at a longer life. For all pressurised systems including other brands; at the nozzle level I do not expect any extra pressure in the supplied ink but maybe 1-3 cm water column gravity of the ink buffer at the head. The Epson damper membrane, the HP butterfly valve, will even out ink pressure to the local air pressure and that system + sensors will control the ink buffer content. It could be that Epson has less buffer capacity than the HP heads have and that the supply tubes interfere more on the ink buffer stability. I can hardly believe that it would be done that stupidly.
The 10000 still had a 180 nozzles per inch head, we are now on 360 for most of the Epsons discussed here. It is getting more critical. My vote goes to the wiper systems making the main difference between the printer models. On the HPs there is no rubber spared to get it right, has to wipe more than 1000 nozzles per channel/inch on heads like. The Canon doubles that.
Met vriendelijke groet, Ernst
http://www.pigment-print.com/spectralplots/spectrumviz_1.htmDecember 2014 update, 700+ inkjet media white spectral plots