I've had a 2560x1440 27" for a long time and recently switched to 4K scaled to 2560x1440 and the difference is absolutely crazy. Everything is so sharp and crisp, letters look so much better, way easier on the eyes. And that's with plenty of people on here claiming that macOS does a bad job downscaling by non-integer values, not that I'd notice anything wrong. I remember my first retina laptop screen felt just as crazy good.