Personality has many elements and contributing factors and, whilst scientific criteria has contributed greatly to our understanding and treatment of personality disorders, it is still an area of subjective assessment. The reason that a person wants a "good personality theory" is also a factor in finding the best scientific means.
Any personality theory must be able to reflect on the complexity of any person as a whole and how he or she interacts in his or her surroundings.
Most scholars now agree that personality is determined by a combination of both genetics and environment, and that neither is solely responsible for personality.
Temperament has a biological basis and as a person develops, various emotions and self-regulation emerge contributing to the development of personality. Even the theorists themselves would have been subject to various factors during their own upbringing such as their socio-economic background, religious beliefs, education, family circumstances, etc. This would render their theories, whilst having a scientific basis, to be partially subjective dependent upon the emphasis and importance of the various factors in their considerations.
Employers often look for personality theories to help them make good decisions. Their methods are sometimes flawed and the best candidates do not get selected because their personalities do not operate well under these conditions.
Personality theories cannot always predict behavior but are effective at measuring and explaining it and for this purpose empirical validity would be , in my opinion, the most useful as there is much data to study and consider and it has been gathered over many years of research. It is useful because it measures behaviour in more than one context. It also removes some of the subjective material as it is a statistical tool.
Some theorists appreciate heuristic value which includes a trial and error element or a combining of results to ensure consistency. Although useful, depending on requirements, it is not always reliable. As reliability is crucial heuristic measurements may be inaccurate. It is useful when decision-making must be fast and provides quick estimates of personality expectations using the assumption of a 'best answer.'
One of the difficulties with comprehensiveness, especially as it relates to the old school theories, is its attempt to cover a wide range making it vague and difficult to test.
A modern theory can combine all six criteria, placing emphasis according to the purpose of the theory and the need to measure personality.
It is also very important to ensure the results are analyzed by a professional to ensure full value is received from the test.