From Crutchfield's website:
"Component video connections are found on most DVD players and HDTV tuners, and on a growing number of TVs and A/V receivers. However, this type of connection can vary in bandwidth from unit to unit. To pass progressive-scan DVD signals without noticeable softening of the picture, a component video connection should have bandwidth of 12 MHz or higher; passing HDTV signals without softening requires bandwidth of 30MHz or higher. If you are only slightly shy of the required bandwidth for the signal you're viewing and your TV is 36" or less, the picture softening may be extremely subtle, or even unnoticeable. "
FWIW, I am running both my HDTV cable and DVD through the component connections on my XR70 and it looks exactly the same as running it straight through.