I don't know if there will be any PQ diffference but D15 IS the name of the VGA connector (don't know where the 'H' in HD15 comes from).
VGA is RGB and the sync pulses are usually carried on Green. So I would bet that the adapter is just wired to send the R, G, and B to each respective wire of the component connection and the sync pins on the D15 are wired to the Blue or Green. It
should be the same as D15 to D15 but who knows?
Try it and let us all know.
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