Also worth considering that the limited bit-rate of the HDTV capture will result in loss of detail to a further extent than the Blu (especially if some of those bits have to go to representing the grain).
That would certainly have been the case, if the DNR on the bluray had not been so heavy. The example I posted earlier makes this very clear:
WOWOW matched to DVD:
Bluray matched to DVD:
The amount of detail lost in the water is quite stunning.