Riichi or Damaten? (2)
This second page on the riichi-or-damaten question looks at cases where the wait itself is already good.
A "good wait" means a wait that is easy to win on.
Ryanmen and other multi-sided waits have many winning tiles, so tsumo is easier to expect.
Even honor-tile shanpon and honor-tile tanki waits can sometimes be very easy to win on.
Example 1
Example 1 is a shanpon wait on and , and both of those are tiles that come out relatively easily.
So this is a good wait.
Even though it is only four tiles in total, it can be easier to win on than a mediocre ryanmen.
Now suppose you have a good wait like a ryanmen, and the hand is worth 5200 or less.
The conclusion comes first:
"In a neutral table, all such hands should be riichi."
Example 2
Draw 
Dora 
In the past, there was a famous rule of thumb:
"Pinfu only should be damaten."
The dominant view was that there was no point in putting out a 1000-point riichi stick just to turn a 1000-point hand into 2000.
But it is now understood that riichi pinfu has an average winning value of a bit over 3000 points.
So even after paying the riichi stick, it is still not a loss.
Even pinfu-only should be riichi immediately.
That is the modern theory.
Example 2 is the same.
Whether you cut or , the correct answer is immediate riichi.
Example 3
Dora
Some hands can improve into Sanshoku or Ittsu in one draw.
Example 3 is such a hand.
But the only tile that changes it is .
The chance of drawing that one specific tile is low,
and much more often, the winning tile comes out before the hand ever improves.
So choosing damaten here just to aim for Sanshoku is a very bad trade.
The one han from riichi, plus ippatsu and ura-dora potential, is the more reliable value.
Example 4
Dora
Example 4 is a slightly altered version, and here there are two different Sanshoku improvements: 234 and 345.
Even so, waiting for improvement is still worse.
Because even if the hand does improve into Sanshoku, you still do not get the yaku unless you win on the high tile afterward.
Rather than waiting for an uncertain two-han upgrade, immediate riichi after tenpai has the higher expectation.
This is especially true for hands like pinfu + one dora or tanyao pinfu.
These two-han hands are considered some of the most efficient hands for gaining value through riichi.
So no matter how many improvements exist, immediate riichi is still better overall.
Example 5
Dora 
Example 5 has a great many possible improvements:
That is five different tiles.
With an extreme case like this, damaten is at least worth considering.
But it is still a rare kind of example,
and even here, immediate riichi is completely fine.
There used to be a lot of talk in mahjong about the "final form" or the "highest form" of a hand.
But these are not very meaningful concepts.
If you were to insist on waiting for the so-called highest form in Example 5, it would probably look like this:
But in reality, you usually win before the hand ever gets there.
Do not get attached to the final form or the highest form.
If riichi is better for the hand, then riichi it.
Theory
Good-shape tenpai should basically be riichi immediately.
Ignore the possible improvements!
Original Japanese page: http://beginners.biz/reach/reach03.html