The State ID is set up through your local county. I think they cost more and you have to wait longer to receive the ID. They also have your records on file. (though it really isn't an issue).

The other card from the PIDC (formerly known as the OCBC) is a just a 3rd party verification service that shows that you have already been verified as a legitimate medical marijuana patient. They won't ask for any medical records or anything... just your doctor's recommendation.

Both are voluntary and not necessary.