On a 23 inch monitor at 1080P you will get a sharper image than at 1680x1050 at 22 inches as the PPi will be greater, more pixels per inch. So you will get a sharper picture when sitting closer as most of us do with PC's.
At 27 inches the PPi is noticably less so you could even end up noticing the Pixels if you are sitting too close.
For a PC station scenario where you are close the 23 would give you noticably better image quality than the 27 but if you have roon enough to be about 4-5 foot away from the screen th e27 will be fine as once you get enough distance between you and the screen it will look better. Pretty much the same as teh 23 close up.