I have the UltraFine 5K but the 4K is similar in this regard: the integration of brightness control + color accuracy.
It's a huge convenience to be able to use my keyboard's built-in brightness controls to adjust the UltraFine's brightness. At night, I like dimming it a bit to reduce eye strain and get less blue light. In the morning, I raise it up again. On a traditional monitor, you have to use the monitor's built-in controls, which are almost always terrible, and force you to use your hand in weird ways. I would basically never adjust the monitor brightness prior to the UltraFine.
Second, color accuracy. If you have an Apple laptop or iMac, you're used to the default color profile of that display, but when you get a third-party monitor, the colors are almost always going to be skewed off from that baseline you're used to. The LG UltraFine is pretty much identically calibrated. It's one of those things you don't really appreciate until you start using it.
The UltraFines are *way* overpriced, but if you're in front of a computer all day for professional work, it's worth it to me. I'll still always hold it against Apple for not making a first-party display with their usual aesthetics, but I'll take the current solution over third-party monitors any day.
