I'm saying two things:

- A 4K monitor has less DPI than a "retina" monitor, so you still see the pixels, thus it's not like someone took a 27" cinema display and doubled the pixels.

- Two 27" displays feel 'worse' to me: While it seems like dual 27" displays would be able to display more, I can't use them both horizontally because my head has to pan too much. And if I switch them to portrait, it's hard to fit two editing windows side-by-side in 1400 pixels comfortably.

So I like the 4K better than the 27" (or dual 27") setup I used before.