When connecting a television that accepts video signals of 480i, 480p, 720p, and 1080i, is fed a signal from a Sony PS3 playing a Blu-ray DVD, it is my understanding that the best option is to set the PS3 to 720p output because this would mitigate the number of conversions (interlacing/deinterlacing/scaling/etc.) taking place before the video signal actually appears on the television screen for viewing (or would it be better to set the PS3 so that it automatically determines the appropriate signal?).
Given that the PS3, as well as the more capable upconverting DVD players (such as the Oppos and Denons with Faroudja chipsets) are capable of upconverting standard (480p/i?) DVDs to 1080i/720p, which will then be played on the plasma screen in 720p, is there any advantage to using a Blu-ray DVD with TVs that only display 720p? Would the quality not essentially be the same if both are being played in 720p? Perhaps the Blu-ray will deliver superior audio through the AV receiver (which could be reason enough to go with the Blu-ray DVD) but as far as the video, would there be any difference?
How about with an LCD TV instead of plasma; that shouldn't make a difference should it?
Normally, it is best to feed a TV a signal that is closest to the format of the TV. Thus, a 720p signal is usually best for a 720p TV, and a 1080p signal is usually best for a 1080p TV. The reason being, when a TV is fed a signal that is not its native format, it must convert the signal to its native format from whatever it is fed.
However, since you are talking about upconverting DVD players, as well as true HD, what will work best depends upon the upconverting abilities of the various particular devices. Thus, if you have an upconverting DVD player and a 720p HDTV, it may turn out that the TV does a better job of converting the signal to 720p than the upconverting DVD player, in which case it would be best to set the DVD player to output SD resolution instead of an upconverted signal. What one should do is try both ways, and see for oneself what is best, and then use the best way for the particular equipment being used.
And no upconverted DVD looks as good as true HD, assuming, of course, that we are talking about viewing the material on an HDTV, and are not so far away that one cannot see details. This will even be the case if you buy what appears to be the best upconverting DVD player ever made, the Oppo DV-983H (which, by the way, uses something better than the Faroudja chipset used in what was formerly Oppo's best player). In other words, if you are viewing the material on an HDTV, and are not far, far away from the TV, you will be able to see the difference between a good Blu-Ray disc played on a Blu-Ray player and a good DVD that is upconverted on the best upconverting DVD player ever made. The Blu-Ray disc will look obviously better (again, assuming one is not too far away from the TV). The reason being, of course, that an upconverted signal cannot magically create detail that is not in the original. But some, of course, make better "guesses" for what should be there than others, so that there can be a considerable difference in quality from one upconverting DVD player to another.
And you are right, it makes no difference whether we are talking about LCD or plasma, or, for that matter, any other type of TV.
Now, as a side issue, which you did not ask about, if one had a 1080p TV, and a device that could output 720p and 1080i, but not 1080p, often, it would be best to select 720p because of the frame rate. However, it may be better to use 1080i; it all depends upon the particular equipment we are talking about.
