>Since I have never had one, what are the advantages of having one 4k monitor vs two 22-23" monitors (which I have now). I don't have room on my desk for the 3rd >monitor. So, if I buy a 4K monitor, it would have to replace the existing two.

>My question is, what is or are the practical advantages?

I tried using a very large 4K monitor and I was disappointed in the end. There was no issue with monitor. It worked very well. The issue is how I program. On a two monitor system I would open the editor on one screen and then run the app on a second screen. Worked well looking at the code and comparing what it actually looked like on the screen. But with the large 4k monitor I was constantly adjusting the windows for the two activities. You say that does not seem like a big deal. At first that is how I felt but it soon became a torn in my side. I end up replacing the large 4k monitor with two smaller (4k) monitors. Yes that was a large expense.
Johnf