The books, including Ray's, and the video's tell the story. Old time players tended to stand higher. Also their "level cue" tended to be three to five inches higher at the buttcap than the tip rather than the all out effort to get the cue as flat as possible.
I have shot both very low and more erect. There was a twenty year break between the time I was getting low and obsessed with pool for ten years and the time I came back and had to stand more erect. I once got so low on some shots that I used my bearded jaw as an anchor point for the cue to slide on.
No question that old school players were highly skilled with the higher stance. No question I shot better with a low stance but the hours put in might have had more to do with it than the stance.
I think the lower stance might not be better but it is easier to use. When you can't get low the shoulder is much freer and the pendulum stroke is much more difficult to execute well. The pendulum stroke and low stance go together. If you use a pendulum stroke you should use the lowest stance you are comfortable with. If there is a lot of shoulder movement in your stroke standing a little higher might be an advantage.
Consistency is the most important thing. I believe that the low stance and pendulum stroke is easier to learn. Almost anything you can do consistently works well. I noticed one of the best in the world has a pretty pronounced chicken wing. Perhaps we should tell him his technique is poor!
Hu