The form that is commonly used is Hanmi maegeri. If you execute Maegeri and step through, as you do in Ido Kihon, your body will automatically turn Hanmi when you extend your leg and step through. You can also say that in case of Ido Kihon, Hanmi is the most natural way to kick.
Reach and ease are two obvious advantages of Hanmi maegeri. It is after all more difficult to execute Shomen maegeri, because you have to stop your hip while it takes its natural course.
Your body will be in a vulnarable posiiton. We explain in the video how this occurs and will show you with an easy to understand example.
Shomen is the place in the front of the temple where the Kamidana (also called Kamiza) is located. The Kamidana is exactly in the front, you look straight towards it. That is why Shomen is often used to describe a posture whereby the hip points straight forward. A more physical name is Mami
If I am not mistaken, the above is one of the quotes of John Cruijff, a famous football player from Holland. I think it is a brilliant quote and it also applies to this topic.
The moment that you execute Shomen maegeri, you have to accept the loss of reach, but you get a stronger kick and position in return. In the video you can see how this affects the ability of your oponent when he tries to bring your off balance.