I was getting a TV for my daughter. 1080p was the rage 720p was one or two years older. I found after doing research that you would need at least a 55" sceen to maybe see the difference. Now that is TV and these are phones. I think everyone makes too much of pixel density. The answer is simple go to AT&T and hold a 920 and an 820 side by side at normal viewing distance with the same screen shot or photo and decide for yourself.
I am going to do this even though I will probably get an 810. I also have to check out this ridiculous weight issue with the 920.