I've seen that graph before! ^ :)
I'd go for 1080p if you can afford it - it's the native res of high def movies, and once the prices start to come down for the players, you might want one.
It's not as bad as it was a year or so ago when 1080p really inflated the price of tv's vs. 720p.
I have a 42", and it's not too hard to tell the difference from 6-7 ft as long as nothing is wrong with your eyesight.