It probably depends. Often, like in the case of the recent Bob Dylan SACD releases, the red book re-master is clearly sonically better than the originally-released CDs. But I don't think that's always the case...there are probably cases where the red book layer is an afterthought in terms of the quality of the remaster and/or pressing. And then there are the conspiracy theorists who believe the music companies intentionally make the red book layer on hybrid SACDs worse, so that A/B comparisons between the two will make SACD look that much better (for the record, I am not one of those theorists!).