4K resolution
So while 4K UHD sounds like it has a pixel structures with 1/4 the area of 1080p, that does not happen with pixel shifting. Only a true 4K projector offers that level of resolution. That's why "true" 4K projectors cost so much more than 4K UHD projectors with otherwise similar feature sets. They produce smaller pixels, finer resolution, no compromising of detail or color from overlapping pixels. By comparison, the slight difference in aspect ratio between DCI and 3840×2160 pixel displays without overlap is insignificant relative to the amount of detail.
5K resolution
In comparison to 4K UHD (38402160), the 16:9 5K resolution of 51202880 offers 1280 extra columns and 720 extra lines of display area, an increase of 33.% in each dimension. This additional display area can allow 4K content to be displayed at native resolution without filling the entire screen, which means that additional software such as video editing suite toolbars will be available without having to downscale the content previews.