Rumor has it that a tape by Zi Wei San He Si Hua was stolen from the Imperial Palace. The thief had stolen the San He band but omitted another band about Si Hua Zi Wei Dou Shu ("ZWDS"). When the emperor found out, he instructed his imperial astrologer to create a fake version and leave it to the citizens.
This may be the reason why the San He system is based on two old books entitled The Complete Book by Zi Wei Dou Shu and The Complete Collection by Zi Wei Dou Shu. Some of the differences between them are obvious.
The Si Hua ZWDS remained in the palace until just before the fall of the Qing Dynasty, when it became open to the public, and is therefore clearly a much more exclusive study system.
Are they different?
A good practitioner should integrate both systems for more comprehensive reading because the basic diagrams are the same for both systems and the strengths of each system are still different.
The San He system uses more stars (up to 108) and is determined by combinations of stars in different areas to derive a very comprehensive reading. The Si Hua system, on the other hand, is heavily dependent on the energy dynamics of the trajectory of the 4 transformed Lu, Quan, Ke and Ji stars in order to obtain a measurement. Therefore, it can use far fewer stars, to be exact, 18 to read it. I am one of the rare practitioners who integrate the practice of hybrid of both systems and use 37 stars for analysis.
A direct result of this is that the latter system requires less memory work, but more difficult visual inspection of the trajectory of these transformation stars. When the trajectory is brought into the picture, there is also a better indication of the energy level and is therefore useful for event prediction. In comparison, static readings from star combinations that are typical of the former system generally give up the event prediction for the qualitative reading. In general, students who are more visually gifted and learn intelligently (because they have fewer star combinations) prefer the latter system.
Both systems should be used interchangeably to provide more reading and forecasting clarity, although I firmly believe that a destiny advisor will provide more value to clients by telling them the timing of an event rather than the qualitative characteristics of matters or events .
In any case, historically the Si Hua system was an exclusive practice of the imperial court until the fall of the Qing Dynasty, while the San He system was propagated by citizens. This historical perspective adequately explains why there are many more Zi Wei Dou Shu practitioners of the San He system, but not necessarily a better system.