Straight from GameTrailer's mouth regarding the videos: "We don't create these videos for the fanboys. That's not the point. We create them so that people who own both systems can be a little more informed on which version to buy. It's the fanboys that turn the comments section for these videos into a debacle. As for using RGB or adjusting the white levels on the PS3, that completely defeats the point of these videos. We play both systems on default settings with the same cabling. If we were to adjust the settings on the PS3 to make it look better then we'd be sacrificing the integrity of the video. It's not the other way around."
So what they're saying is that they aren't taking advantage of the PS3's full-HD capabilities. It's built for that. But they aren't using it that way in their videos. Either crank both up to their maximum potential or get out, we say. Feel free to leave your thoughts as well.
[Update 1: Took out an uninformed sentence regarding Xbox video output. We apologize for the inaccuracy.]
[Update 2: Gametrailers offers another explanation here.]