I have both a 1920x1200 screen and a 1920x1080 screen.
By far and away the extra vertical resolution is the better option. Obviously the 1200p screen cost more, but it's worth it. (I am a programmer, so screen real estate is important).
For a 27" screen, the higher resolution is what makes it worth paying more for. Otherwise, I would much rather get a cheaper/smaller 1080p 23/24" monitor.
I must say that if I were not a programmer, then I would not need the extra resolution.
I think I saw a deal not long ago for a 1440p, 27" screen for around £300. I would've bought it, if I were looking for a 23"+ monitor.
With regards to the Benq 27" monitor, it should be commercially available in August, so I guess we must wait and see what price it sells at. There are other 27" monitors (with higher resolutions), already available though - if you are desperate to buy one.