A 27" 5K is 218 PPI, which is the minimum pixel density for desk work, IMO.
I completely disagree with that. 110 dpi is totally fine for desk work. Always has been and will probably continue to be for a really long time.
I take my 38" doing 3840x1600 at 110 DPI over a 27"K (or even two) doing 218 DPI any day.
Now if you do photography or work on designing bills (as in money), then you'll want higher DPI. But for "desk work", there's zero need for anything more than 110 DPI. It may be "nice" to have retina fonts but it's by not a requirement.
I'd even say the real world is powered by something like 95%+ of people doing "desk work" on 110 DPI (or less) screen.
Also, if 5K / 218 PPI is the "minimum pixel density" for desk work, what's the minimum density for creatives?
By "desk work" I mean the type of work where the physical distance between your eyes and the display is ~50cm. Mobile devices like phones have higher pixel density because they are held closer to the eyes (~25cm) than a computer monitor on a desk. Angular pixel density is the important factor here.
As kitsunesoba mentioned, I find >200 PPI much easier on the eyes when reading and writing text, my eyes don't get nearly as fatigued as they do on low PPI displays.
I think it's one of those things that once you get used to high PPI displays, it's really hard to go back to low PPI. Have you looked at a pre-Retina iPhone or iPad recently? Would you take that over the high PPI display common on every mobile device today?
Personally I wouldn't take an ultrawide over a high PPI main display and "regular" PPI second display but that's purely a matter of preference.
