The HP longevity for color is something like 3x the permanence of Epson Ultrachrome.
And more importantly, the HP pigment set remains very closely color balanced as fading progresses. When fading does eventually occur, the image remains more natural looking, getting a little lighter and losing some contrast, but still retaining plausible tone and color. Canon's set is less well balanced, and Epson's Ultrachrome set(s) much less so because the Ultracrhome yellow which is common to all the Epson pigmented sets is a seriously weak link. It would be good to have an alternative yellow to the current Epson UC yellow. I feel strongly enough about it, that I will soon be dedicating my Epson 3880 to a hybrid ink experiment.... substituting the UC yellow for HP's yellow pigment using a third party refillable ink cartridge filled with HP's yellow ink. With a better yellow like HP achieved, the Epson UC ink sets would indeed be on a par with HP regarding longevity performance. The UC yellow is the problem.
Canon's LUCIA EX set is harder to characterize on longevity, but land's closer to HP in overall light fastness than Epson, the green ink being the weakest and the yellow ink being second weakest, but the green doesn't get used for skin tones or low chroma colors so overall color balance remains superior to Epson as fading progresses. Moreover, relevant to this thread is the fact that what Canon calls "red" is actually orange (with a hue angle of about 45 degrees, i.e. ideal for replacement of yellow and magenta when making skin tones) so skin tone fading performance is improved as well (though not as good as HP's performance) because the Canon red (aka orange) is more lightfast than the Canon yellow ink. As others have noted, I suspect Hp's "red" ink is more orange than red as well, but I can't confirm since I don't currently have an Hp Z printer in my lab. Easy to tell for sure if the printer calibration target lays down separate channels of ink.