I have a 30" DVI cable from my Samsung TS160 to Toshiba MT8 front projector. I originally had component hookup, with 20 ft cables, and DID have artifacts on fast moving sequences. I changed to DVI, and signal has been flawless. One comment, however. As my projector is a fixed panel display (DLP), the DVI keeps the signal digital all the way to the projector. On a RPTV (other than DLP or LCD), signal is processed as analog so you will not see a difference between component and DVI, as peid has already mentioned. You should have no problem with either 20 ft component or DVI connection.
'On CRT displays', The very first circuit your DVI signal hits once it enters the display is the DVI decoder where the outputing signal is Y, Pb, Pr (component). From there it gets treated the same as your other component inputs. This is the same for most of the TV's I've calibrated and seen.