Hey Wings,
It sounds like there is a setting within your outlook that causes the sync to happen periodically. With IMAP emails, the inbox on your computer mirrors Webmail, so the process to send/receive isn't the same as a general POP3 setup.
You can use either way of setting up the emails, neither is preferred over the other. It really depends on your personal preference.
Generally, changing from IMAP to POP3 will require the deletion of the original settings and starting fresh with the alternative settings.
Brodie