Personally I would say it is a great upgrade from the BenQ, definitely even some "wow" moments. I sold the BenQ to my housemate so I can still pop back and forth to compare the two.
Viewing angles are much better, I would notice much different contrast from the top and bottom of the BenQ, there is barely any on the LG.
The picture "pops" from the LG much better than the BenQ, it really feels more like a picture in front of you than a monitor.
The all round image is crisper, richer coloured and better contrasted. The backlight is very low key, it turns completely off when the screen is black, which is a strange effect but shows how dark it gets. And in general black looks much more black and uniform.
What I would say is that out of the box the image on the LG was not looking as good as the BenQ, I like my screen very bright. I did a lot of tweaking and it went from being an ok upgrade to an awesome picture.
Here is what I did to the settings:
Brightness 100
Contrast 100
Sharpness 5
Black Level Low
Response time Normal
Gamma 0
Colour Temp Medium
RGBCM saturation to 72 individually
And just a tiny boost to vibrance in windows.
Having the gamma and black level low combined with the high brightness/contrast and saturation balance each other out so the image is not compromised at all.