The difference between the two is the Yin Yang Five Elements Bagua theory and prediction objects.
1. Qimen Dunjia mainly studies the Yin-Yang and Five Elements Bagua theory, while Fenghou Qimen focuses on the study of the functions of wind and water. For example, Qimen Dunjia predicts the direction of things by analyzing the combination of Qimen and Jiugong, while Fenghou Qimen predicts the changes of things by observing the behavior of wind and water.
2. The prediction objects of Qimen Dunjia are relatively broad, including personnel, wealth, health, etc., while the prediction objects of Fenghou Qimen are more specific, mainly in Feng Shui and meteorology.