I remember reading a magazine article by Massad Ayoob several years ago covering just this topic. Being a LEO, Mr. Ayoob apparently (Open) belt carries most of the time. He also advocated using a stall (next to the wall, if possible) whenever using a public bathroom. As I recall, he was taught this by one of his students, who he gave full credit to. I remember thinking he (Ayoob) must be a pretty good guy to give credit where it is due. I've run into plenty that didn't, and I've never been impressed by them.
Regards,
Dave