Nevermind this helped:
There are a lot of variables to take into consideration... What type of content you're watching, how large your screen is, how the media was originally recorded/transfered, etc.
In general, 720p handles a lot of movement better, but 1080i has more resolution.
1080i gives you a native image this size: 1920x1080 (2,073,600 total pixels on your screen per frame)1080i needs to scan twice per frame, so within 1 frame it throws 2 "fields" equalling: 1920x540 (1,036,800 total pixels on your screen per field)720p gives you a native image this size: 1280 x 720 (921,600 total pixels on your screen per frame)So you get a larger (or better resololution image from 1080i, but because it is interlaced (meaning each frame actually consists of two fields) certain fast movements may appear to stutter or just not look smoothed out to the eye. Also, since most of us cannot detect that resolution difference with our naked eye (on screens AROUND 50" and smaller) they tend to look very similar in the end. And depending on what you're watching, you may (or may not) notice any difference in moving content.
A lot of people say 720p is ideal over 1080i in gaming situations because 1.) content is usually moving fast and progressive scanning handles movement better and 2.) 1280x720 is "enough" resolution for most sized sets out there. Some math can show you that on anything smaller than a 65" monitor the human eye can't tell the difference in resolution between 720p and even 1080(i or p) (at normal viewing distances).
From that linked article:...
In other words, the ideal viewing distance for a 42" 720p display, for example, is 7.7 feet. If you view it closer than 7.7 feet, most people will be able to see individual pixels, but at distances further than 7.7 feet, you can't see them. In the case of a 42" 1080p display, the ideal viewing distance is only 5.5 feet--beyond that, you can't see the pixels and you can't really appreciate the full resolution of the display. In other words, it would be virtually impossible to distinguish between a 42" 720p display and 42" 1080p at distances of about six feet or more. Given that many people view their televisions from 8-10 feet away (if not even more), you would have to have a 65" or larger screen to really notice the difference between 720p and 1080p.
Bottom line: If you're playing on a 50" monitor or smaller, theres really going to be no real difference that you can tell in picture quality... You *may* find you prefer the look of one over the other... and that might even change depending on what you are watching or playing.
As you creep up above 65" in screen size, you're going to notice the "blow up" of the smaller 720p image, so there you'd likely prefer the larger 1080i picture (or better yet, 1080p).