I have a 3840 x 1600 as my main gaming display
I have a 4K in portrait as my productivity display.
The only issues i have with a 4K is the font size being so small even on a 32inch.
I can feel my age, because im sure when i was younger this was not an issue.
Also 4K's have pretty horrible scaling. Meaning, you use your 4K @ 4K, and not downscale it.
My next monitor will be the 55" Samsung Arc which is also 4k. I will replace the 32inch i have in portrait, as i am pretty sure TV's do not like to be mounted sideways, hence why i can not throw in a LG C1 on portrait. Also TV's stands do not allow it, and i do not want bolt down a wall mount in my room, incase i decide to move my desk somewhere else.
But there is a lot of real estate difference from 2160p to 1440p.
However you also face a new can of worms called do you even have the GPU to support 4k, unless you intend to do no sort of 3d on that 4k monitor.