Casey, if you didn't read it when it was cited here before it'd be worthwhile to study the results from the listening tests, blind and otherwise, which
Home Entertainment Magazine ran on the various audio formats which may be present on Blu-ray discs. The DD and DTS tracks are in fact of a higher standard than those present on regular DVDs and the tests indicate that they have the capability at least as a format, if handled properly, to sound essentially indistinguishable from the TrueHD or Master Audio tracks.
In the cases that you describe, if the DD and DTS tracks were noticeably louder than their cousins on the regular DVDs, that alone would make them sound better apart from any format superiority, and mixing a little louder doesn't require a better format.