Dunedin,
Component is not "RGB in composite-like cables".. Thats a common misconception and its not true..
RGB is RGB where as Component is Component. They are completely different.
Actually, Component is more like S-Video than RGB.
The confusion comes from the fact that Component has Red Green and Blue connectors and this leads people to think that its RGB.. But its not.
RGB is made up of Red, Green and Blue composite signals, where is Component is made up of Chrominance and Luminace signals. (Like S-Video)
Calling RGB is correct, as thats what it is.. But component should really be called Y, Pb(Cb), Pr(Cr).
In terms of quality, Component is awful, S-Video is better, and the RGB and Component are superior again.. Whether RGB or Component is better, is open to debate.. They are equally as good, but generally Component should be slightly better..
Basically, as long as you are using RGB or Component, you are getting the best you can get out any device.
And, as you said, you can get Progressive Scan over Component, which you can't do over RGB.