The DISC profiling or the PI are both inventories of personality and natural inclinations. They trap the person by asking numerous questions, many alike, to check consistency. Then, the auto formatting of records happens, and it requires trained personnel to read and map it. Once done, it gives a graphical cut on the individual's natural tendencies, applicability to the job, the fitment of his or her positives and negatives, and sort of helps anticipate certain behaviors.
Having had a DISC done on me, I can say it was as accurate as possible - in fact, some home truths were so astounding it took me days to accept I was indeed like that. I'd say it was as close as close gets. It will help in hiring, profiling, and also L&D.
Regards, Seema