(Crazy that there were/are people who claim she couldn't act when you see the number of emotions in her eyes in a split second.)
Yes, I think one of the reasons some of Joan's performances have aged better than some of Bette's is that Bette's bitchy bravura tends to be one-note -- literally, one-note, in that Bette's vocal intonation tends to be high-pitched and nasally.
But Crawford knew, and recommended to other young actresses, that you need -- especially as a woman -- to drop your vocals down, at least here-and-there, to deeper levels in order to keep the audience listening; otherwise, 24/7 higher-pitched warbling will cause the viewer not to take you seriously.
It makes you seem more in-the-moment, more engaged. As a result, Bette Davis was often more-mannered and felt more on-automatic in a way Crawford was never really guilty.
This was also partly due to Joan's sense of being inferior to Bette (and Bette being in agreement). Joan was often trying to get Bette's approval and acknowledgement because Bette was one of the only women in Hollywood who had superior status over Joan, and Bette always rebuffed Joan for exactly the same reason.
But Bette was resting on her own laurels, sometimes phoning it in -- and phoning it in with that high-pitched nasal streak. While Crawford, goddess bless her, didn't do that.
