Microsoft blogger Ozymandias tries to explain the real difference between 1080i, 1080p and 720p. For instance, a 1080p resolution has 2,25x as many pixels as a 720p resolution, and you’ll have to spend 55% less time on each pixel when 1920×1080 compared to 1280×720.This is because the level of detail stays the same, while only the amount of pixels increases. He says that most games won’t be able to run 1080p without sacrificing in other areas, like texture details. This could explain why the anticipated PS3 launch title Resistance: Fall of Man will only support 720p.

Most games can’t justify running at higher than 1280×720—it would actually make them look worse because of the compromises they will have to make in other areas.

So a 1080p game probably won’t have any extra details or effects compared to 720p, but will render the same image at a higher resolution. He also mentions that rendering 1080i and 1080p is the same, since both resolutions have the same amount of pixels.

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