ddrueding
Fixture
The smaller the pixels the better. Of course, this is overridden by the more pixels the better. Having pixels that are infinitely small, and therefore the edge of a letter can be exactly where it needs to be, is ideal. Provided, of course, that the screen is of the physical size you want.
Within the 27" size, 2560 > 1920.
Within the 27" size, 2560 > 1920.