Quad HD vs Full HD: What’s the minimum you should buy in 2020?

It wasn’t too many years ago that the smartphone resolution wars were in full swing. The debate raged over whether Apple’s Retina Display jargon actually meant anything, while Android phones raced from Full HD (FHD) to Quad HD (QHD) resolutions. Sony even went as far as to push the 4K narrative for our tiny phone displays. Fortunately, that’s a mobile trend that hasn’t caught on (yet).
In a complete U-turn, the industry today is much more relaxed about the display clarity argument. In fact, a couple of new high-profile 2020 releases don’t bother with the flagship QHD resolution that we’ve become accustomed to. The Motorola Edge Plus and LG Velvet are content with “just” FHD+ resolutions, as is Huawei’s P40 series.
Do these handsets offer an inferior display experience or has the industry settled the Quad HD vs Full HD debate and picked FHD+ as the clarity sweet spot?
Do you really need Quad HD?
The selling point of Quad HD displays is sharper images and improved clarity. This is more important for larger displays, where a greater number of pixels are required to keep up the pixel density and thus clarity. Pixel density is often referred to as the pixels per inch or PPI number. A higher display resolution also helps games appear smoother with fewer jagged edges. Although rendering more pixels puts more strain on the graphics processor, potentially lowering the frame rate and/or consuming more power.
However, there is a limit on the level of detail that the human eye can see for a given viewing distance. There’s a lot of variables to the science behind human visual perception limits , including the size of the screen and viewing distance. For a small 5-inch smartphone, an FHD resolution has you covered pretty much regardless of how close you hold your device. For larger 6-inch and 7-inch handsets, the move to FHD+ to Quad HD can make a little bit of a difference at closer viewing distances.
The graph below plots roughly the maximum pixels per inch you can see for a given distance in yellow. I calculated the PPI for these distances using the equations you can find here . The PPI offered by various resolutions for three unique display sizes is shown in the column plots.

Columns above a line represents crystal clear clarity at that viewing distance.

For devices between 6 and 7-inches in size, the crisper density of QHD is just about noticeable when holding phones closer than 30cm from your eyes. The key takeaway is that higher resolutions are only just noticeably better on the very largest phones held very close up. However, most consumers probably don’t hold their smartphones so close. 30cm to 40cm is nearer to a typical handling distance so even FHD has you covered virtually regardless of device size at those sorts of distances.
It’s also worth noting that wider aspect ratio FHD+ displays found in modern devices sit as a nice middle ground between...