For an example many of you may already have in hand, the Latino Spanish track on Star Wars Despecialized 2.5 was recorded without the Dolby decoder. It's still the best-sounding track we have of that particular dub, so we still use it, but you could A/B dialogue-free sections of that against the English 1977 mono mix to get an idea what the difference is (levels, dynamic range, recording quality, etc, may also be different for unrelated reasons).

I guess I should ask if -1 plans to re-capture the Latino Spanish audio with the Dolby decoder. I think that was the plan, but you know how things go sometimes...

EDIT: Also, you know, if there's an audio genius with access to lots of high-end software who can simulate Dolby-A through software... uh, PM me ;)