The Mi 6 packs a 5.15-inch IPS LCD with a resolution of 1920 x 1080. This is a fairly modest display by today's flagship smartphone standards, as you can easily get a 1080p IPS in an entry-level phone these days with most companies opting for 1440p screens instead. However, Xiaomi clearly feels 1080p is perfectly adequate for their flagship, and they'd prefer the increased performance and battery life afforded by the lower resolution.
At 428 PPI, the Mi 6 display still looks great despite its lower resolution. Naturally it's not as crisp as top-end 1440p LCDs, however the LCD used here is still very sharp for viewing text and imagery, while the near-indistinguishable gap between fingertip and LCD provides a lifelike experience. Viewing angles here are also very good for this type of technology, with minimal color and luminance shift at off angles.
Xiaomi claims this LCD is capable of 600 nits of peak brightness, and I easily validated this claim during my testing (in fact the screen is slightly brighter than this). Xiaomi also uses some marketing fluff about "negative LCD displays", whatever that means, to describe the excellent contrast ratio of this panel. Again, the Mi 6 performs extremely well for an LCD in this regard, almost topping our charts.
For some bizarre reason, Xiaomi talks about the Mi 6's NTSC color gamut reproduction, despite the fact NTSC isn't used in Android and really no one across the industry uses it. The good news is this display performs well in color performance out of the box, covering 99.9% of the sRGB spectrum with surprisingly solid default accuracy. The screen is a bit too cool by default, however it comfortably beats most other high-end smartphones in accuracy. And the display still looks fantastic while doing so.
Even better, Xiaomi includes a display mode called 'standard' (which isn't the default mode, by the way) that improves upon the already solid out-of-box performance. The main advantage of this mode is how it corrects the white balance to essentially dead accurate, which in turn improves greyscale performance. Color performance isn't impacted as significantly, though in this mode the Mi 6 still sits right near the top of our accuracy charts.
From this perspective, the Mi 6 is a very solid option for those that need a near color-accurate smartphone display, or just don't want something ridiculously oversaturated. It's one of the best and brightest LCDs on the market; the only major downside being its lower resolution than some competitors.