Difference between receiving a reference or a Ptr in a callback

Old ROS1 issue, and I made a test, the result seems no performance difference.
Cannot login ROS answer anymore. I wonder whether I missed something.
ROS2 everywhere.
difference between receiving a reference or a Ptr in a callback
https://answers.ros.org/question/81241/difference-between-receiving-a-reference-or-a-ptr-in-a-callback/
test