In my opinion firmitatis is the most important to the triad. The structural integrity and stability is the most important because it allows the building to stand upright. The second most important is utilitatis. The buildings utility, particularly what it is used for allows a building to serve its purpose. The least most important in my opinion is the venustatis, referring to its beauty. The beauty usually holds little actual importance to the actual form of the structure and is rather to make it look better.