I like the extra screen space 4K offers; but only on large screens. I run without any scaling (well, 100%), my editor offers 101 lines visible vertical and 470 columns. (each line is ~1/4" measured on a ruler; 27" screen 23" from my eyes)

I can view ~6 open files at once (more depending), and this can be very helpful when trying to remember context: instead of remembering, I just split the screen and open the same file again.

When I got a 4K monitor, it replaced my previous dual monitor setup. I now prefer just one high-res monitor. Only disadvantage is that I spend time tweaking font sizes, but that's mostly front-loaded and once it's set up (Linux) I don't even think about it.