Actually, placing two documents side-by-side requires at least 1920px width to be useful. I challenge you to try to put two documents side-by-side on a 1440x900 laptop screen and have both still in readable font sizes. Now, at 24+" displays with 1920px width, it's a different topic, but most people still have 22" range and even at 1920px width, things will just be way too tiny to be read side-by-side.