^ This is where it's at imo, if the panel is for gaming, highly depends on what type of gaming genre you like.It really depends on the game. Top-down games where the same features slowly pan about are noticeably better with high DPI displays. Civilization, Crusader Kings, Diablo-likes etc. But shooters? You will hardly notice.
....
I've never worked on a 4k screen, but I would think it is most important if you do lots of desktop work, either like lots of real estate or a very crisp image. 1440p @ 27" (or in my case the double on 49") is fine for me and have no interest in 4k, for the same reason as you state.I didn't note anywhere about discussing what video card you have. Games will run far worse at 4K than they do at 1440.
Really, I cannot think of any reason to go with 4K, outside of content creation. I have had 1080, 1440, and 4K displays. I no longer have any 4K displays. But sure like my dual 1440s.