It seems that HDtvtest over in the UK prefers CS1 as well and has a good explanation of what they see in the review of a PDP4280XD and PDP508XD. It seems that although the Color points in CS2 are more accurate there is a higher level of desaturation from 0-75% compared to CS1.
Quote from HDTVtest review of PDP4280XD:
"The manual suggests that [Colour Space] 1 on the Pioneer PDP4280XD is optimised for a more vibrant colour reproduction: indeed the colours were somewhat over-saturated when plotted against REC 709 (reference for high-definition colours) on a CIE chart. The default [Colour] value of -6 in [Movie] mode led to an undersaturated gamut for [Colour Space] 2, but one would expect to correct this easily by bumping [Colour] up a few notches and then mapping the primary and secondary colour points to REC 709 using Pioneer PDP4280XD's colour management system"
"Talk about making the wrong choice when faced with a 50-50 decision. I went with [Colour Space] 2, thinking that it's more likely to conform to standard colour gamut... after all even the manual describes it as "standard colour reproduction"."
"Looks promising: all the colour points on the spot, with the intersecting lines converging on D65. Surely this is it?"
"Sadly, even after calibration [Colour Space] 2 actually threw up some disconcerting colour decoder inconsistencies, and 0% to 75% saturation depletion. Because the [Colour] control on Pioneer PDP4280XD affects both colour saturation and intensity in uncertain proportions, it was not possible to fix one without spoiling the other. [Tint] and [Colour Management] mainly alter hue and so were of no use in my attempts to rectify the saturation/ intensity errors."
For Ken:"Note: Colour decoding error cannot be gleaned from a CIE chart. It is generally detected through real-life material, filters or less commonly, colour intensity measurement."
"Up against a brick wall yet again, I abandoned [Colour Space] 2 and plumped for [Colour Space] 1 to calibrate the colours from the ground up:"
"On surface this looks worse than the chart for [Colour Space] 2, as the red, green, yellow and cyan colour points are mildly oversaturated. However, the colour decoder and 0% to 75% saturation aberrations that I encountered in [Colour Space] 2 are now totally gone, making [Colour Space] 1 the undisputed gamut of choice. One for the pub quiz?"
Clarification 19 July 2007: The above only applies to HD (REC 709); for SD content you should still use [Colour Space] 2. "
The basline color charts are quite close to the uncorrected CS1 and CS2 color spaces that I measured on my 150FD
Here is the link for the full review.http://www.hdtvtest.co.uk/Pioneer-PD.../Benchmark.php