ASUS ROG Swift OLED, 27 inches at 1440p
The monitor we sit at ourselves. OLED means black is really off, not dark grey. You see the difference in the first minute and never want to go back.
27 inches at 2560 by 1440 is the point where pixels disappear without the graphics card breaking a sweat. The same size in 4K hardly looks better, but costs roughly twice the computing power. That is why this combination is here and not the biggest number on the shelf.
What OLED really brings is not the contrast on the spec sheet, but the response time. A pixel changes colour in a fraction of the time, and so a moving image stays sharp instead of smearing. Anyone coming from a normal monitor first takes it for a higher frame rate. It is not.
Two things honestly belong here. OLED can burn in with image content that stays unchanged for hours. The devices clean up regularly by themselves, and manufacturers now give a warranty for it, but if you display the same spreadsheet eight hours a day, you are better off with IPS. And OLED only reaches full brightness on parts of the screen, not the whole picture. In a sun-drenched room without curtains you notice that.