This is a quote from a review of one of the few retail players with RGB out. The Sony 533D.
The RGB output does have certain advantages in NTSC in that it acts like a Y/C (S-output) might and cleans up the spurious colour side effects of the signal. Cross-colour - the colour 'rainbow' effect on areas of fine detail - and cross-luminance - the crawling colour dot movement on sharp vertical edges - are all suppressed in the RGB mode. On the Sony test disc Tune-Up A.V. there is a specific resolution grating in Chapter 4 to show the worst effects of cross-colour. On a conventional composite output into a non comb-filter TV the grating is invisible as it is obscured by a mass of coloured dashes. The 533D, via its RGB output, reproduces this grating perfectly, with no false colour information whatsoever. This sort of performance should be attainable with a TV containing a comb-filter, but that Tune-Up A.V. grid has been previously tried on a conventional player through a comb-filter NTSC TV and the suppression of the cross-colour was nowhere near as effective. Without doubt, the 533D playing NTSC discs in RGB mode produces much cleaner images than via the composite output.