I'd throw out the Samsung 19" (only 1440x900 resolution) and go with the 20". The 19" asus might look a little better because of the better dynamic contrast and smaller pixel pitch... but it shouldn't be THAT much of a difference. You get the extra 1" of real estate with the 20", which also has decent specs.
For reference:
http://en.wikipedia.org/wiki/Dot_pitch
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