Riyan-Men ＞ Kan-Chan ＞ Pen-Chan (The Basics pt03)
Check Mahjong No Jan-Ryu for the original article.
*Translation of the original article start below*
"A Riyan-Men Wait is Dominant by Far"
In Mahjong there are 5 different types of waits, and the wait that has the most tiles to wait on is the Riyan-Men wait, as you can see in the image below. If you compare the amount of tiles you can wait on to the others, you can see that it is double.
Although a Shan-Pon wait gives you 2 different tiles to wait on, you are using 4 of them within your hand, so the maximum amount of tiles out there will be 4 tiles. Either way, a Tanki wait has a disadvantage simply by the amount of tiles possible.
Of course, someone else might be using the tiles you need, or they may already be discarded, so the actual amount of tiles that are available are most likely to be less than what was explained. Although it doesn't mean that "more possible waits means you will always win", it's good to keep in mind that a Riyan-Men wait is dominant by far.
"Comparing a Pen-Chan Wait and a Kan-Chan Wait"
So which one is more dominant, a Kan-Chan or Pen-Chan wait? If you simply look at the amount of tiles you can wait on, they seem to be the same, but if you think of the possible change to a Riyan-Men wait, the difference is a lot bigger than what you may think.
As you can see with this example, a Kan-Chan has more advantage to become a Riyan-Men wait compared to a Pen-Chan. It is important to understand the "Possible Changes and Think of How it will Change" in Mahjong. We will learn that even within a Kan-Chan wait, there are certain shapes that are more advantageous over one another next time.