I posted this on another forum in response to an inquiry, but I thought some might find it useful here.
I own both. We have plenty of feedback already on the basic analysis (such as roll vs no roll; build quality; etc.), so I won't go into that. I will share my personal experience based on my personal needs. I don't need to sell either, so I hope you'll view my opinion as being unbiased. I am new to Canon, and have used Epson for more than a decade.
Full disclosure: I am very particular about color and sensitive to it. Moreover, I do a lot of portrait work, particularly where light tan to medium skin tones are involved. I am so specific about the nuances of color, that I never felt satisfied until I could truly control the color management process from end-to-end (i.e., I use custom camera icc profiles as well as custom icc printer profiles). Today, I am proud to say that I no longer need to worry about the technical process. I worry only about my images, and I know the output on the printer will be what I envisioned in my head and edited on my PC.
Playing Fair: I use the same papers in both printers. I have custom profiles for both printers made by the same company (Chromix). While I could print directly out of photoshop, I actually print using Q Image Ultimate. The main point is that I am printing the exact same image under the same conditions. The absolute only difference between the two prints is which printer driver I select (Canon or Epson).
My Experience: For basic printing, or if you are not very particular, or even if you are (but print mainly landscapes and such),....either printer might be good enough. They both have exceptional output. However, for me, there is a nuance in the Canon prints I have grown to prefer. With flesh tones, I find more natural life-likeness, and tan skin tones don't have that slight green tone to them that they do on the Epson. I am not sure what it is, perhaps its the red ink, perhaps it is that it is newer technology. I have done countless blind tests, and for the types of photos I print, I always pick the Canon, regardless of paper, and rarely do I need to do any more than glance at them for a second. To be fair, for landscape-type photos, I do often have a tough time telling them apart, although I don't do a lot of printing of that type, and a landscape photographer might appreciate the bigger gamut of the Canon.
Generally, I think that the Chroma Optimizer is a bonus for the Canon. If you don't like auto mode, you can coat the whole page. You can also configure a Media Type that matches your needed media type, but that turns off Chroma Optimizer completely.
For black and white, I use the black and white modes of each printer. I have found that they are close, but in blind tests, I almost always pick the Canon. Note that they are both excellent, but the canon gives me a "very slightly" more natural gradation from black to white. Moreover, I have found the Canon edge to be B&W image dependent in some cases.
I find the Epson P800 paper feeding options to work perfectly well, including the front fine art feeder (once I learned to use the front feeder's "front lip" to align the paper). Therefore I did not find the Canon feed system to be a "big" advantage, although it is excellent. Note also that the Epson roll holder is a big plus, but I am not doing much roll printing these days.
I have found tech support for both to be great, but Canon has US based tech support and it feels a little more personal (I assume it is not a gigantic team).
Caveats: I find the various margin limitations on the canon really annoying. For example, you need a minimum 1 inch margin at the top and bottom for Fine art paper, and its minimum top/bottom margins for glossy paper are uneven (I think they are .10" and .20"). Note that these are generally only annoying when you print on Letter size, as it is noticeable at that size. Also, this is not the printer for you if you print roll paper.
Conclusion: No ink switching (shame on Epson for not addressing this after all of these years), exceptional portrait quality and skin tones, the accounting manager, and the ability to configure media types has won me over. I have not found the Canon to use any more ink than my Epson. I am impressed with the Canon technology and I want to reward that. I owned 7 Epson photo printers over 10 years, and while there were incremental improvements there hasn't been much innovation.
The Canon is now my primary printer. I still have both as I am in no rush, but I am unlikely to keep the Epson for the long run. It doesn't make sense for me, economically or otherwise, to have two 17" printers.
Custom Profiles: I highly recommend custom profiles. They are beneficial for both, but are needed more for the Epson. Depending on the manufacturer, and even then on the particular profile created for a specific paper by that manufacturer, their profiles will get you anywhere from 70%-90% to end-game. Custom profiles get you 100% there and let you pick papers based on you preference or based on matching the paper to the image. You will never avoid a particular paper because the image is off due to color management issues.
