updated 21 April 2022
I just want to just share my personal experience in using different resolutions of different desktops.
Before the pandemic, I was satisfied with my HP Stream netbook. That is just too low in specs and the screen is, of course, too small. But nowadays, during the pandemic, we are forced to do online classes and all work is done through the computer. So, this one really matters now.
First, I simply project the netbook to an external monitor 27" 1080p. Then, we were provided by our company with the iMac 21.5", that's 4k Retina Display, knowing that we really need that. Plus, there are two external monitors, 19.5" 1080p and a smart TV 42" 1080p.
With these too many screens, I realized these things (for productivity):
If that is really 1080p, then, that's good. You have a lot of space. With Windows OS, you get a scaled view of everything. They say Windows OS is not good at being scaled but I think it's just fine. When you compare that to MacBook Pro scaling, then it's not that good.
But here is one thing you achieve: you have a bigger projection of everything, especially when your eyesight is poor.
Viewing distance is a little bit farther since the projection is bigger. But still, it is a good one. 4k resolution is not so good for poor eyesight so that Mac provided the option to lower the resolution thereby making all things appear bigger than the default.
Also, some external 27-Inch monitors are already curved. This actually has no benefit for this size. The 27-Inch iMac is still not curved. But beyond this size, you need a curved one.
If you have 20/20 eyesight, then, you'll find this 4k Retina Display an awesome experience. There is only one catch: make sure you have the correct viewing distance.
I'm not mentioning any specific distance, but the basic rule is that you stretch your arm then find the correct spot there whether moving away or towards the monitor. It was just I came from the larger scaling of 1080p and Windows OS, I realized I should be closer for this display. And once I have my spot, the experience is actually good, I don't experience much digital eye strain.
And since they say it's retina display the individual pixels are too much, you will not see any individual pixel, no matter how close you are. This one really makes a striking difference, for example, when using GitHub and you are editing the document right there at the site, you'll see that even the fonts are too small in editing mode, they are not problematic if you have a normal vision. Compared to 1080p, the 1080p is a little bit bigger, but you can see the individual pixels. In my experience, I can say it's not as dense compared to the Retina Display of iMac. That really matters.
This external monitor is not completely a computer monitor, no matter how it is claimed to be. Also, it's not just the 42-Inch. These displays are more for viewing videos and hence cannot be used, say, for text editing. It can be, but for sure, your eyes will not be able to handle it for a longer period. Even if they claim a 4k 50-Inch screen, computer monitors tend to be more expensive, so from the price alone, you can say it's not really a good quality even if manufacturers insist it's 4k resolution.
This 42-Inch Smart TV is projecting the iMac, but still is not good quality for productivity. Again, let me emphasize for productivity. It's good for viewing because you have a very large projection. So, you can use larger TV screens for viewing videos on YouTube while you are working, say, playing a music video or live concert. You just saved money for a larger projection of videos. That's an awesome experience too, again, for viewing videos.
Even if say, it's purely 4k like the iMac screen, still you tend to watch videos farther. So, 4k, for that reason, does not really matter. If you really want to pay for it, just make sure that you have the correct viewing distance.