Dandxg, you are dealing with pixel size differences. the 19's are native 1440x900, 20 native at 1680x1050. the screen size diff is 1" (diagonal).
a 1.05% size increase, verses a pixel diff of 1.16%
Now if you were to hook up a 22" at 1680 x 1050, (1.15% size increase), I am willing to...