The only possible difference that you need to be aware of is that some displays will only accept a progressive (ie. non-interlaced) signal via component, but that's down to their electronics rather than any inherent difference between the two types of signal.
What I am thinking of doing is passing HD video from the PC to the Crystalio via component cable and letting the Crystalio process the video. I will keep the VGA cable connected directly to the Pioneer, for browsing & documents etc.
This will be an interim measure until the next generation of HD media players become available.
I have a Lumagen HDP fed from a Pioneer 868 interlaced HDMI (producing a superior PQ to that from the PC even when running FFDSHOW et. al), but when I use the HTPC I feed 720p out of the PC via DVI and thus use the Luma in pass-through mode (with a little colour correction), which is similar to what you're planning to do so am interested in what processing you envisage for the scaler.