The HR24 and H24 have a setting that allows you to choose whether the box sends all signals at a specific resolution or at the native resolution of the broadcast. DirecTV has channels in 480i, 720p, 1080i and 1080p for some VOD. If you have a 1080p television, you can tell it to send all resolutions to the tv at 1080p, using the box to upres anything less than 1080p. You can also set the box to send the signal in its native resolution and let the tv take care of the up or down sampling. Sounds like you have it set to native. The setting is in the "Menu" and (I think) "Setup & Fav's". Check your manual or head over to
www.satelliteguys.us. This is pre-school stuff for those guys.
Most TVs don't up and downsample as well as most DVD players, BR Players and receiver boxes, so most people are better suited to setting the output on the receiver. If you have a high quality TV, though, it may do it better than the box. Only your eyes can make that decision.