Nice arguments. I would agree to larger is better and found 800 to be wanting as you would have to squeeze everthing into a constricted space. Most of the major players are now switching to what you see is what you get, meaning if U use a small screen everthing is small and if you use a larger screen all images and fonts are larger. As Varsili pointed out the display resizes automatically to the viewing screen. This in itself is good as analogue display monitors are dirt cheap and even lcd displays are getting cheaper by the day. I am using a 17" AIC LCD flat screen monitor which cost me M$650.00 which is USD 185.70. Eventhough I have a good laptop, I still prefer to do all my work on my PC simply because it is faster and the display is larger. More and more people can afford to buy larger displays for their computer and I would think that eventually the sales of larger displays will supercede that of the 15" screens and manufacturers will focus on 17" and above to beef up their sales. It will be difficult to cater for every need and to please everybody.
Why waste the spaces on the two sides, you can fit a lot of ads and affiliate links into the two empty spaces.
So I say larger is BEST.