huh? 1080i has a resolution of 1920x1080 interlaced, or an effective resolution of 540 progressive lines.

720p on the other hand is 1280x720, with 720 progressive lines.

they're VERY different. the best, and probably settled standard for the next few years is probably going to be 1080p, as more and more movies are mastered nativly into that for HD DVD and Blu-Ray.