I have been trained by teachers of both methods. The teachers of empty chamber said that they taught EC for liability reasons.
There is much truth in this statement. Apart from competition or personal preference, there are other reasons to teach C3 carry that many here may not encounter. As a training manager, I am also one of the few in our area that is certified to teach Armed Security guards in our region. There are Security companies that MANDATE that their guards carry pistols in C3. So guess what, I have to teach them how to be effective while carrying in C3. While many here may not like the idea, C3 carry is more common than most can imagine.