I have the same problem, the quality of images generated from api directly is simply much much worse than the one from bing image generator too. Even when I take the revised prompt and then feed it to bing! It is almost as if openai has put a limit on dalle through api, to encourage user subscription to chatgpt+.
EDIT: I am not yet sure if this is 100% correct, but from what I can observe it seems to be a bug with style=“natural”. DALLE3 API poor quality even considering prompt revision - #4 by 1004wsh Which style did you use?