It has always made sense to me that a 720 signal sent to a 720 screen should look better than a 1080 signal, i or p, sent to a 720 screen, especially if the original video is not 1080i or 1080p. No matter what else, 1080 to a 720 screen requires an extra conversion step.

One detail, too, please: when you have a screen with 768 lines, are all of those lines actually visible? Old TV signals ran at a frequency that was 525 times 60, meaning there were 525 "lines" and which we called 525 lines, but there was also a small amount of time in each field that was blank...we call those signals 480i today, implying that 45 lines weren't actually visible lines.

Are all 720 lines viewed? Are all 768 lines viewed?

I'd think converting 720 lines of video signal to 768 lines of display would be a difficult conversion.