PROMPT_COMMAND has the following flaw: a command gets recorded as soon as it has finished. So command which never finish (e.g. because they run for a long time, and the user closes the terminal window, or reboots the system) never get recorded. Another flaw: the users starts a long-running command in terminal window 1, and immediately they want to start a variant of it in terminal window 2, but it's not available in the history.
PROMPT_COMMAND has the following flaw: a command gets recorded as soon as it has finished. So command which never finish (e.g. because they run for a long time, and the user closes the terminal window, or reboots the system) never get recorded. Another flaw: the users starts a long-running command in terminal window 1, and immediately they want to start a variant of it in terminal window 2, but it's not available in the history.