I'm using a 43" 4k monitor and it has changed the way I work quite fundamentally. Screen size no longer being an issue let me use the center of the screen for what I need to see in detail and the borders for interfaces. The big downside is that I've had problems calibrating the screen accurately.
Whether you choose 4k or 1440p should depend more on the specific model you are looking at, but I strongly advice against buying a 1080p monitor. I would never be able to go back to one.