I have always used the 50/50 method - along with the tightly pulled lips - I guess it's called the 'smile' method. I did not know there was anything else until I joined this forum a few months ago. Since I am an inveterate experimenter, I decided to try different methods just to see if I could detect anything that worked better.
When I first started playing again, my entire face would tire very quickly from using the smile method and I could not play anything until I had rested. Of course, as I worked at it, the practice time increased gradually but the high notes (above about top-line F) would still fade after just a few minutes. So, one day when the fade had set in, I decided to try some things other than 50/50. I tried 2/3 top and 1/3 bottom and could not blow any notes at all. Then I tried 1/3 top and 2/3 bottom and found that I could hit the high notes that had faded only minutes before - and, in fact, even higher notes that I could not reach (like high E). I tried this on several occasions to ensure that I had eliminated other variables and found that it worked consistently. The problem was that I could not play the low or mid range notes with this method which meant that I would need to change my position in the middle of playing to use it on high notes only - not good if the music involves a fast run from low to high notes - or vice versa. So, I have not adopted that as a permanent embouchure change.
However, at the same time, I tried another change. Instead of keeping my lips pulled tightly across my teeth using my cheek muscles, I let my lips relax slightly and push into the mouthpiece a little ways. I had read about the 'pucker' method but could never make any buzz with my lips fully puckered (like I was going to kiss a baby).
However, the formation that I adopted was more what I would call 'pursing' my lips - I'd say it is like positioning the lips to spit out a watermelon seed. When I analyze the effect, I realize that with the smile method, the buzzing happens right at the boundary between the skin around the lips and the soft mucous membrane of the lips. When I use the pursing technique, the buzzing moves back maybe 1 or 2 mm into the fleshy part of the lips. Also, the tension on the lips is maintained by the muscles around the mouth rather than the cheek muscles. This placement is back to the 50/50 top/bottom that I started with.
With this technique, I can play high notes much longer without tiring. The high and middle range tone is good. The low range tone is not so good but I think this is because I also moved from a very large mouthpiece to a very small one at the same time as it seemed to help the tone of the high notes. The low tones are gradually coming along so when they are back to full status, I think I will have a new embouchure which improves my endurance, range and tone quality all at the same time. I am still working on making it a habit as I tend to revert to the smile method when the music is complex and I can't consciously focus on the embouchure. But, so far I am encouraged.
I hope this helps anyone who has a question about this.