Legal Question in Criminal Law in California

From a practical standpoint, there isn't much difference. The two offenses are charged in the alternative, which is District Attorney-speak for "let's throw everything at the wall and see what sticks."

Penal Code 487 is grand theft. It is a wobbler, meaning it can be charged as a felony with a maximum sentence of three years in state prison or a misdemeanor with a maximum of a year in county jail. Under Penal Code 487(c)(1), stealing an automobile is grand theft, no matter what the value.

Vehicle Code 10851 is taking a vehicle without authorization. It is also a wobbler with the same sentencing range.

The big difference is that PC 487 requires the thief to have intent to permanently deprive the owner of the stolen property, but VC 10851 requires intent to permanently OR temporarily deprive the owner.

That makes 10851 somewhat easier to prove. There used to be a joyriding statute with less serious punishment, but it now only applies to boats, not cars, motorcycles and other motor vehicles.