Re: Yeah, brilliant!!
If you're using a sub 10" screen to watch video... then it really doesn't matter one iota if it's served up in 480p or 1920p, because the human eyes ability to accurately distinguish between the two is severely diminished at that scale.
What matters more is the DPI than the screen res.
Neither of those two statements is true.
To take the second one first, what matters is DPA (dots per arcsecond [of vision]). That changes with the distance of the screen from the eye. This is why "jumbotron" type screens at sporting arenas and advertising venues can use individual light bulbs (as low as 0.5 DPI depending on the specific type of bulb) and still create high resolution images -- the screens are far enough away that each light bulb occupies ~50-100as of vision.
Now to the first: my 5" phone, when held about 1-1.5 feet from my eyes, occupies about the same space as my 50" televison across the room (and about 1/2 the width/height of my laptop screen 2.5 -3 feet away.) I can clearly make out the pixels on any of those screens at a 480p resolution at those distances. I can even make out the pixels at 720p. At 1080p, the pixels are hard to see, though still visible on my laptop (the largest in terms of arcseconds at the distance I keep it.)