I often get his question from fellow practitioners, students and public which one comes first or which is more important.
Forms here means the formation of water and mountains. so in simple terms the geographical terrain and so in modern terms roads and buildings. The essence of it is to know how Qi moves and where is the vibrant area.
VS 
Formula refers to what is being measured by the Lou Pan or the Feng Shui Compass. How the result is largely dependent on which school of Feng shui is the master from and from there the Feng shui master decipher the reading. There are only a handful of orthodox Feng shui schools but within each school there are hundreds of variations or versions but never mind that for now.
On the other hand, formula tells the master what kind of Qi is in the house. Some practitioner puts less emphasis on forms but more on formula because formula give faster felt effect or visible result to the clients. Well this is the age of instant noodles right? Everything has to be fast..fast…fast….However, this is not what I believe and I would like to share with you a saying I once read:”Life is like sex, if you want a good ending, don’t rush.”
Those who champion forms argues that without forms no Feng shui can be strong or lasting and without form how can Sheng Qi(beneficial qi) be tapped. This is what a famous celebrity master teaches.
Essentially he is saying that Flying Star is used for internal of a house while it has to be supported by San He land forms outside. All I can say this is just pure marketing or he is not familiar with Feng Shui. San He is San He, Flying Star is San Yuan. Perhaps his study have not reach the required depth in San Yuan.
The truth is in using them in harmony. Formula tells us what is likely to happen in the house after we know what Qi is present in the house and then the effect on the people living in it. Forms tells us when and how good or bad is going to be. This is what San Yuan advocates.
Forms have strong and lasting effects and formulas tells us the remedy that is necessary to harmonized the house with the dwellers. So one must understand the implication of how forms can benefit the house and in what way (told by the formulas). One can also use the 81 combinations as part of the formulas for diagnosis purposes.
No need to argue which is more superior, you just need both to get it right, at the right dosage!. The only difference is Forms you cannot change it or more difficult but formulas, yes you may change the configuration of the house and you can change the Qi in the house which is much easier to achieve. This is the goal of Taiji, harmony in Yin Yang. Is this not what Feng Shui is about?
Please visit www.fengshuimechanics.com for more information.