Besides screen size, resolution is another relevant spec to consider. 4K, also called UHD or 2160p, is the highest of the most common resolutions for monitors and televisions. It is precisely 3840 pixels wide and 2160 pixels tall and gives you four times the pixel count of 1080p.
In terms of resolution, usually more is better. The more pixels a screen has, the sharper the displayed image is. As a tradeoff, higher resolutions require more power from the source to drive all those pixels. Due to this tradeoff, 2K monitors became very popular with PC gamers.
Video game consoles work a little different. They are highly optimized systems designed for a specific target resolution. Current generation PS4 Pro, Xbox One S, and Xbox One X offer support for 4K games and video, and upcoming next gen consoles scheduled to release late 2020 are specifically designed to run at 4K or above. If you also consider the vast amount of 4K video content available, it seems like buying a UHD display is a safe bet and a future-proof investment.