...ah, much discussion in the Pioneer plasma threads, but it seems (if the facts hold true) that in fact the scaling in the Pio's (at least the Elites) is actually better than the REON.
So, yeah, 480i>HDMI>Kuro would (hypothetically) be better than 480P/720p/1080i>HDMI>Kuro for SD material.
Furthermore, while 23.997p>HDMI>Kuro would be best, it seems that 1080i>HDMI>Kuro would be better than 1080p>HDMI>Kuro for HDM sources, as the Pio again will do a 2:3>3:3 advanced pulldown, rather than having the 2:3 cadence "burned" into the 1080p/60 signal.
Finally, as above, the only way to get 480i from your HD/BD player is to switch resolution from source to source, you can't tag SD as one res and HD as another easily. Plus, many players (like my OPPO) won't transmit 480i over DVD or HDMI, only the progressive signal (ie., not the "raw" interlaced signal on the disc itself)
Man, I'm sickened that I know any of this...