If you have a newer SD set with component / s-video inputs, HD will look much, much better than SD. A lot of SD sets have a horizontal resolution of over 700 lines through the component or s-video inputs. Broadcast analog TV only has a horizontal resolution of 336 lines, so HD through the video inputs can look at least twice as sharp. If a DVD looks better than SD programs on you set, then the HD channels will look better than SD version.