The short answer is very little as far as its effect on your goal - to eliminate from public view your criminal history._ The technical answer is that a sealing does not require certain agencies to actually "destroy" their records whereas a court order expunging records does._ Additionally, if the case was not dismissed by the court or "dropped" by the state attorney's office then the statute requires that your record be sealed for ten years first before it can be expunged.
Most law enforcement agencies destroy their physical records after several years maintaining only an electronic record of the arrest._ The Court Order will require that agency to remove the remaining electronic record from public access.
A backround check of a sealed OR expunged record will show NOTHING.