Repeated rankings from industry related experts on here who have posted are:
1) DVI
2)VGA
3) Component
4)SVHS (which is 480i ,and also available over component, and is what 99% of dvd's are made in)
I run both VGA and DVI current from 2 LG HDTV tuners, so its very quick and easy to switch them around. I have to say, between DVI and VGA on HDTV signals I can never see any difference whatsoever. I have never swapped it out for long periods of time, but thats my opinion.
It's also possible the source signals are so good and close to my plasma's native display properties, that in this case the difference just doesn't show up enough to be seen.
Several members have posted recently about the DVI connection image quality being better for them over VGA.
There are technical posts on the board about it why DVI is best, if you dig hard enough. The basic reason is the video stays in the digital domain I think with DVI.
I have watched CSI via both and simply see no difference at all. One of my HDTV tuners is also an HDTV PVR so I have been able to replay the exact same scene or pause it and swap the connection see no difference.
BTW, feeding your tv the 480i, over component, if it has a good internal scaler is often the best way to go, that way you get ONE final coversion to your displays exact output resolution, not more conversions along the way which lose data for resolution. This known but often forgotten fact is resurfacing all over the board recently due to the explosion of scaling dvd players , and the discussion of upscaling its caused.
You dvd player MAY have a better upscaler, it may not, but keep in mind if it doesnt upscale exactly to your displays resolution then you introduce another conversion along the way.