In the iTunes 10.6 preferences under Store, you can select whether HD downloads come in 720p or 1080p resolution. In the iTunes Store, movies conveniently list the file size for the selected format. A couple of examples: Hugo is 1.74GB in SD, 3.99GB in 720p, and 4.84GB in 1080p. Monty Python and the Holy Grail is 1.00, 2.91, and 3.65 gigabytes, respectively. However, to determine the quality difference, I looked at two (currently free) TV episodes: episode 1 of season 5 of The Big Bang Theory, and the first episode of Awake.
The Big Bang Theory Season 5 Complete 720p Tpb 5
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