What type of T.V. do you have. Just look at your T.V.s specs and it tells you what resolution you have. On most HDTV's you have to know what you have. Some T.V.'s HAVE two component outputs, one will give one resolution the other another. The DVI input will give another. Some people are so stuck on what my t.v. WILL REPRODUCE. yOUR T.V. will produce the best resolution it can. I don't know to many sets that are just 1080i, most likely they are 720p (Progressive, which is alot better in terms of speed of objects like in baseball (Reality based) If you see a ball hit at normal speed, there is a difference in the 720p and 1080i (Interlace). However most people donot even see the difference. It is all based on your T.V. i HAVE A ps3 and a XBOX 360...and I have a few T.V.'s one produces 1080p the other 720p..Also within those it does have other resolutions of course. Once you hook up the PS3 AND XBOX 360, IT will tell you what you can and can't do in terms of resolution. It's all on what you like to see.. Most T.V.'S suppport several formats. hdtv's that is.
To answer the question, it's important to understand the difference between 720p vs 1080i. A 720p signal is made up of 720 horizontal lines. Each frame is displayed in its entirety on-screen for 1/30th of a second. This is know as progressive scan (hence the 'p')The quality is like watching 30 photographic images a second on TV. A 1080i signal comprises 1080 horizontal lines but all the lines are not displayed on-screen simultaneously. Instead, they are interlaced (hence the 'i'), ie every other lines is displayed for 1/60th of a second and then the alternate lines are displayed for 1/60th of a second. So, the frame rate is still 30 frames per second, but each frame is split into two fields, which your brain then puts together subconsciously.
Most of the time interlacing works fine, but for fast moving images, such as sports like baseball and hockey it can cause problems which manifest themselves as a 'stepping' effect on-screen. Progressive scan signals don't have this problem and so are better suited to sports. (Like I mentioned earlier)
ESPN puts it like this: 'Progressive scan technology produces better images for the fast moving orientation of sports television. Simply put, with 104 mph fastballs in baseball and 120 mph shots on goal in hockey, the line-by-line basis of progressive scan technology better captures the inherent fast action of sports. For ESPN, progressive scan technology makes perfect sense.
Now there are many articles on this issue, just make sure you know what your T.V. can produce, one can also alter the T.V.S settings if you have the service code, each t.v. has this code. You will not find this code in your manual, but you can get it from the manufactured (Not the T.V. SETTINGS) The service settings, most cable guys or T.V. REPAIRMEN have a sheet that might have each T.V.S personal code. Well that enough of this longwindedness. I have tried to address your question by answering it without going into too much detail. It may seem like alot, but it really isn't. I just touched the surface.