Regardless of credentials the best way to know who is good and who is not is seeing the results of their work. Folks who are done and happy, and sporting smooth, care free, hair free skin give the best testimony of a practitioner's skill. Of course, most clients don't want anyone to know that they ever had a problem with excess hair, so that may be hard to find even for the best practitioners out there.
RE and LE both mean that the electrologist has taken the formal test in a state that mandates such a test in order to practice in that state. Note that I don't say that a person who has this credential is practicing in the state granting the credential. Many people working in unlicensed states travel to other states for the sole reason of taking another state's exams and returning home so they can advertise themselves as the "only RE/LE in town". Each state's test and minimum requirements to take the test vary. I would add that if you are an RE/LE practicing outside of the jurisdiction of your Registration/License, then how much assurance is that credential really giving the client? After all, that person is operating OUTSIDE the jurisdiction of that governing body and would not track any information on that practitioner's actions in another state.
The CPE is a test given by the same people who brought you the SAT, LSAT and other great college exams. It is accepted as an international certification, and is only given once a year at a site proctored by the Chauncey Group. It is a very secure test with all security measures taken to assure that the person taking the test is passing or failing based on his/her merits. People sitting in the same room at the CPE test don't have the same test booklet in front of them.
The CCE and PCE are less secure exams given on the same material as the CPE, but are not accepted as being on the same level of integrity for no other reason than the very real possibility of cheating on these tests. They are mailed out over the country and proctored by many different people, as chosen by the person who wished to take the exam. If one can ligitimately pass the CCE and PCE then one should also pass the CPE, however, since the CPE is only given once a year, and only in one location, many people find it a hardship to travel to the place that test is given at the time it is available.
Again, a person who can pass the test ligitimately could have passed the CPE just as easily, but one has no way of knowing who cheated, and who did not.
In the end, other than the fact that a person practicing in a state that mandates an RE or LE but doesn't have one, the presence of a credential only points to the fact that the person voluntarily submitted to having their knowlege tested in the field in book form, and passed. Althoug that kind of action suggests extra care and desire to do the best one can do by one's clients, it is still no garantee that an electrologist with a credential is any better than someone who doesn't have one. One other frequent thing is an electrologist who has attained one of these credentials, who fails to renew it, thus loosing the right to advertise that credential anymore, but continues to practice. As long as the state one practices in does not require a credential to practice, this is perfectly normal behavior.