Ok so I'm so, so late as always.
I just watched the Japanese voice with English subtitles of AC. My first thing was, does anyone know why they have one script for the English voice track and then another slightly different English script for the subtitles of the Japanese version?
I'm 60/40 on the changes that were made. I actually prefer the English subtitles with the Japanese voice track. There were a few changes made when they translated it that I liked.
It seems like whenever Square translates to English, they try to add in "cute" or "funny" twists to the lines when they shouldn't. The Turks were probably the biggest offenders of this in AC.
As far as English voices vs Japanese voices...
AC:
Tifa's Japanese voice is better, has more appropriate emotions. She sounded weird in several places- definitely agreed on the church scene, and I hate when she calls Cloud at Healen and says, "Be careful, okay?". She sounds so bored.
Rude, Reno, and Kadaj's Japanese voices are also better.
I'd say Cloud, Cid, and Barret are about equal.
Vincent's Japanese voice is worse. The voice actor went TOO cold and emotionless. It was kind of like he just straight read from the script, and that was it. I prefer Blum's representation- it's cold, but you get a sense of warmth behind the words. However, I like the English subtitles of Vincent and Cloud's conversation in the Lost City. I think those words work better.
ACC:
I've seen some... I might need to just re-watch it again because now I feel like they went in and changed and added in all this stuff, and now it's more confusing. I like the new voice for Marlene.
Did not like the Denzel flashback. Why on Earth does Tifa ask the strange person on the phone, "are you crying?". That's just un-natural.