The "p" and "i" stand for progressive and interlaced. 1080i is a higer definition picture, but means you get a line of pixels followed by another line, interlaced.
progresive means you get the pixels all at once.
You'd have to have a HUGE LED screen to actually notice the difference between p and i, but I beleieve the difference between 720 and 1080 would be noticable.
We'd definaly have higher def choppy shadows
