Well, chiming in only as an ordinary consumer, and most certainly NOT a video engineer or expert....
I have to confess that years ago when I first converted from the old tube-TV to a 42" LCD, I always ran my TV in full-screen mode, pretty much all the time.
Again, as a consumer, and not a video engineer, I wasn't no interested in all these technical details. The reason I switched to a wide-screen TV, was that I was tired of watching wide-screen movies on my old TV and seeing black bars at the top and bottom. I realized that was to preserve the aspect ratio, I get that. But I hated having half my TV screen black when watching a movie.
So when I made the switch to a wide screen TV I was very excited, so imagine my surprise when many movies STILL showed black bars at the top and bottom! (Granted, smaller than on my old TV but they were still there). That infuriated me, because I still felt like I was paying extra for a TV and still getting empty screen!
So I ran it in full screen mode. After a while, though, I got tired of that too, because for some reason, the picture would switch back and forth to wide screen mode again for certain scenes. Not sure why, if it some coding on the digital track, or something funky my TV was doing, but that was even more annoying than the black bars, so I stopped. And just learned to live with the black bars.
But I tell you, even after all these years (and even though I do understand the whole aspect ratio thing), it still bugs me when I see black bars.
I paid for 42", I want to see all of it! (grouchy old-man mode).