My guess would the that the act of inserting or removing the drive from USB port would result in larger weight difference as the connector contact areas rub on

My guess would the that the act of inserting or removing the drive from USB port would result in larger weight difference as the connector contact areas rub on each other. Depending on hardness of each side you could be either losing or gaining weight. This is excluding any possibly debris falling out or being stuck in the port. Disclaimer, only a fun thought exercise, I know very little about these things.