Loads of laptops have been flowing in advertising resolutions of 3200x1800 (QHD+) and 3840x2160 (4K), seemingly ushering in the new era of Retina-class displays. Sounds nice, right? However, it is important to know that, in many of these cases, these advertised resolutions are not a complete truth.
The "4K Ultra HD 3840x2160" display offered with the Inspiron 15.6" models uses the RG/BW Pentile matrix, a deceptive trick that enables manufacturers to produce a display that can be advertised as a particular resolution, without actually providing the full detail of the resolution. The specs page says 3840x2160, your display control panel says 3840x2160, but the actual display doesn't enough dots to properly display that resolution, so it has to be downsampled. These displays tend to produce fuzzy text, and they lose detail on anything zoomed less than 200%.
Displays like this are not competitive with Macbook Retina displays or other high-resolution displays, and have lower actual pixel density than the 2560x1440 (QHD) and 2880x1620 (3K) resolution displays that are available in other laptops, which don't even require as much graphics processing power to handle. Heck, they're worse quality than some of the normal 1080p IPS displays they're supposed to be an upgrade from, when it comes to color and contrast.
What Dell should have done: Dell should have used a 3K(2880x1620) resolution display in the Inspiron if they did not want to use a real 4K display, since the 3K(2880x1620) displays being used in laptops today (Thinkpad T560, Aorus X5) are better in just about every imaginable way than the false-4K ones: effective pixel density, colors, contrast, GPU load. But Dell opted to deceive its customers instead, giving us a worse display but calling it better, just to be able to market the laptop as "4K Ultra HD".
Laptops known to use fake high-resolution displays:
Laptops known to use real high-resolution displays:
Have a laptop you suspect to use a false high-resolution display, or have access to one you'd like to test? Use this image. Temporarily set your scaling in display settings to 100%, then load up the image in a Web browser and make sure its zoom is also set to 100%. If the display is truly the resolution it advertises, you will not see fuzzing like so.
General recommendations: Be aware of this issue. Seek out "lower-resolution" true-RGB displays over RG/BW displays that claim higher resolutions. Also pay mind to the display in general, because differences between displays tend to have a lot more of an effect on normal use than the differences between most other components. It is recommended to avoid 1366x768 resolution in screen sizes 13.3"+ if your budget is over $350 where 1920x1080 starts to become an option, as 1366x768 severely limits the number of windows that can fit onscreen at once. Choose IPS displays over TN displays for improved contrast and viewing angles.