P8000 vs. P9000 vs. P10000

[Texshooter]

Which of these new Epson 44" printers would you prefer and why? Is having an extra gray channel (P10000) better than having two extra colors (orange/green P9000)? Is having the additional O&G colors of the P9000 noticeably better than the P8000? I'm thinking of upgrading my 3800. I only print photography and have low tolerance to head clogs.

 

[Ink stained Fingers]

I don't think the choice of colors impacts the occurance of head clogs, regular maintenance and a somewhat regular printing cycle should keep the printer running. I'm not specifically familiar with these Px000 models, I can only respond on a more general level.
It had been a trend over the years to add colors to the ink set, the idea is that you can get more color saturation e.g. for skin tones if you have an additional orange available. Typically orange gets mixed from yellow and magenta, with an orange you can get some more color saturation ( and may use a little bit less ink volume since you are not mixing from 2 colors). When you measure and create a profile with such an ink set you will see some (not so much) extension of the gamut volume in this area, so this is measurable. But the more important question is whether it is visible. You would need just these colors in your images which are just outside the gamut without an orange ink, but still within with orange ink, and if you then compare prints you may see a difference - or not. The differences are not drastic but much smaller and barely visible in most cases. Doing such tests is difficult/or impossible for you since you would need to have printers available with different ink sets, or RIP software with an option which ink set you want to run.
The same would apply to other inks - orange, red, green, blue which come in this or that printer model.
I did a kind of similar test some time ago, with and age old R800 A4 printer which comes with blue ink.
And I compared the Epson blue ink against a blue ink premixed with cyan and magenta and filled into a blue refill cartridge. Yes, the Epson ink is slightly more blue, more color saturation, slightly wider gamut vs. the blue mix. But I must admit I could not see differences in prints for direct comparison. I did some similar test longer time ago, Epson was upgrading the Ultrachrome K3 magenta to a 'vivid' magenta as they called it. Yes, there were differences measurable in the gamut, but barely visible in prints.
There is another element which is very important when it comes to printed colors , the paper plays a significant role in this , the gamut size and black level you can acheive with a particular inkset. So colors always need to be viewed and judged together with the paper they are printed on.
So it is difficult to give a clear recommendation, I would tend to use the gray ink option, and not additional colors, I rather would select a paper giving me the best gamut.
The gray ink may be used by the driver for some undercolor removal (UCR) , replacing some of the luminance of a color with gray which places less ink overall onto the paper, and the gray ink may give you some better print options if and when it comes to B/W printing. But all that depends on the driver functionality I'm not familiar with. So this would be my considerations in this situation, but I would
not consider it as a recommendation , you may have other ideas in mind and weigh particular details and information differently.