One advantage of 5K over 4K in the new iMac

Lee Hutchinson of Ars Technica quoting Dr. Ray Soneira of DisplayMate:

"This monitor is designed for video production, which is the primary reason for buying a 5K display as opposed to a 4K display," he said. "A 5K display is great when working on 4K content (3840×2160 or 4096×2160) because you can view all of the images at their true native 4K resolution, which is very important, and then have a fair amount of leftover extra screen space all around it for controls, icons, and even a generous 3.4-inch high text area at the bottom for commands and text input."