Msg#: 4679522 posted 6:04 pm on Jun 13, 2014 (gmt 0)
Overarching rule: Link to the form of the URL that you want people to see and use. Search engines will not be happy if all your internal links lead to 301s. They will also not be happy if the same content is available at two or more URLs, as when a page is reachable at its "real" URL alongside its "friendly" URL.
Is "example.com/?p_id=123" really the WP default? That seems like a horrible, neither-fish-nor-fowl approach.