You do know on most Tv's 720p>1080i right?
1080P>720P>1080i
This is absolutely incorrect if by > you mean better/higher definition graphics.
the 1080 and 720 refer to how many lines of resolution are horozontally across the screen. The i and p stand for how thay are refreshed. i standing for interlaced which means 1/2 at a time (such as lines 1,3,5,7,9 etc then 2,4,6,8 etc). Progressive means all the lines are progressively scanned and refreshed at the same time. So 1080i still has 360 more lines of resolution thus a higher definition picture.
Now how often the lines of resolution are refreshed whether they are interlaced or progressive is determined 100% by your TV...... 120MHz, 240MHz or 600MHz refresh rates (currently only available on plasma TVs) (yes, plasma currently has the fastest refresh rate and clearest pictures for fast moving video)