For people with good vision, a 4K 6" screen held 18" from the eyes will look better than a 1080p screen, all other factors being equivalent. Held further than about 18", 4K won't make a a difference for most people.

For a 60" TV that sits 10 feet away, you're not going to see much difference. Move that TV to 4 feet away, and you'll appreciate the extra pixels.

For virtual reality, and other applications that put the screen much closer to your eyes, the extra pixels will make a huge difference.

It's all about the viewing distance.

At 20/20 vision, we can resolve ~300 pixels/inch at 10-12 inches from the eye. [1]

For a 6" screen, that works out to ~1800 pixels. So maybe not 4k, but the next step down from 4k generally is 1080p, which is less than the figure I gave above.

So yes, there is a point.

(And that's not getting into other factors either, such as panning and stroboscopic effects.)

[1](http://en.wikipedia.org/wiki/Visual_acuity#Physiology)

What's the point of the Nexus 6 having 1440 vertical pixels in landscape mode? Nexus 6's 1440 pixels is a third of the way between 1080p and 4k. So, presumably, scaled down 4k video would look better on it than scaled up 1080p video when the device is held closely.

I swear last I checked the 805 only supported hw accel. VP9 up to 1080 not 4K. The Qualcomm spec sheet says it supports up to 4K but reports out in the wild suggest that is "best case" and it doesn't really work beyond 1080.