I think a lot can depend on your equipment. When using DVI or HDMI the signal stays digital from point A to point B. With component it gets converted from digital/analog and then back from analog/digital. There are times where I enjoy the movie like appearance of component over DVI/HDMI. My Panny S97S DVD player is an upconverting dvd player that gives you 720p or 1080i to my projector. The picture is better over DVI in my situation, but others have expressed minimal difference.
I have a Samsung OTA (over the air) High Def box to pick up local HD broadcasts. It only has component and the picture is fantastic. I bought it before DVI and HDMI came out.
