It's all in your head Neo. The Matrix is playing tricks with your eyes.

But seriously, then why is it that the PS3, by default, auto-detect and sets the video resolution in the ranking of 1080i, then 720p. I also don't see any diff on my 40" Samsung LCD. But my head perceives the 720p to be better.

The 1080i format is more widely supported by manufacturers and broadcasters; broadcasters however would normally broadcast only in either 720p or 1080i but not both. This should not be much of an issue in that any HDTV set you buy should be able to display pictures in any HDTV format by up-converting or down-converting to its native format, i.e. the one in which it is designed to produce a picture.

Theoretically, from a pixel-count perspective, 1080i supports better spatial resolution than a 720p HDTV. In theory, 1080i supports a pixel count of over 2 million pixels as against the 0.92 million pixels supported by 720p HDTV but...

In reality the situation is somewhat different when it comes to an interlaced format. As already expressed earlier on, the difference between the two halves of an interlaced image leads to interlaced artifacts. In order to reduce the visibility of these artifacts, the vertical resolution of an interlaced signal has to be filtered. That reduces the real image vertical resolution far below the number of scan lines (typically 60% of the number of lines), associated with the interlaced format.

Yet there is also another issue against interlaced video, that of digital compression of images. Digital compression of images is more efficient with progressive video at the source than interlaced video. Compression is necessary to make images fit into the space allocated for a broadcasting TV channel.  Further more, 1080i material is limited to around 1440 pixels horizontally, which reduces even more the overall effective resolution of the 1080i format.

The end result: The actual difference in effective resolution between 720p and 1080i is almost negligible.  Further more, a 720p display is capable of a better flicker-free picture when it comes to fast moving action movie scenes and sports.
And what about 1080p? The situation with 1080p HDTV is totally different. The horizontal resolution of 1080p HDTV material is equal to the number of scan lines since there is no need to reduce this as in the case of interlaced material. This means that 1080p supports the full 1920 x 1080 pixels (2.07 million pixels) while at the same time, enjoys the added benefit that all 1080 lines are displayed in a single pass.

In other words, 1080p HDTV enjoys the best of both worlds - it has the spatial resolution of 1080 HDTV material and the smooth stable image of a progressive scan format.

Also don't forget the source image is important as well. You won't see any difference at all btwn 720p or 1080i if the source is rendered as 720p in the framebuffer anyways. If the source is rendered in 1080p, or 1080i movies, then you could see the difference although most of the time it's very minor. 

Since "source image" is important, so we should buy ori XO games! 
Just wonder the pirated source can up to 720p or 1080i ah? or will it as good as ori game? just curious....

Can. What do u think this is.... dvd movie copy from wayang version? LOL 

No wonder i couldn't call u, i forgot ur in Aussie

Anyway Happy New Year bro~! Enjoy the drunken scenes there

bro string,u drink beer ka?!..aiyo!! (just joking around,plz dont take this seriously)

i think u misunderstood. Djinn said there is no difference to the naked eye when he changed his 720p to 1080i