An importance feature to check when considering the size of an LCD screen. The pixels do not always have the same size on all the screens. At some diagonal sizes, the manufacturers just increase the glass surface but not the number of pixels.
This is the reason why the French-speaking Hardware.fr web site made a nice little comparison graph that I re-use here:
All this could have a noticable influence depending on the application you envison for your new screen: photo handling and retouching (you may be willing to have large readable pixels), video games (your graphics card must be able to drive so many pixels or the LCD screen willl have to interpolate up from the low resolution the card will be providing), desktop application (you may be willing to have a maximum number of windws on your desktop, or your reading will be improved by larger pixels).