Personally, I see no difference between HDMI and component from my HR20-700 to either my previous Toshiba 52hm84 720p DLP or my current Pioneer Kuro 5010, when both inputs are calibrated. However, HDMI switchers are fairly cheap and reliable on monoprice.com, so you can be the judge. And, you need a switch, not a splitter (which sends one signal to two displays). Once you get the HD-DVR, try hooking both HDMI (use your PS3 or Xbox cable) and component up simultaneously (they both output at the same time) and switch back and forth, and see if you see a difference. That'll answer your question.
Two things are infinite: the universe and human stupidity. And I'm not sure about the universe. -- Albert Einstein