Let's analyse this with more depth.
Given 2 totally different directions in conceptualising a highest value hand, there are many reasons why it is better to be optimistic on getting 2 doras then to get sanankou.
1. There is a theory that a confirmed 1 han is better than an unconfirmed 2 han. I can't explain specifically why the theory said so but it is popular amongst players that that is the conclusion. From this, although not confirmed, there is a very high chance of getting 1 Dora then to get sanankou. A high chance is because you have
and
to go through. This means, there's 25% that it the hand turns up with no dora, 25% with 2 doras and 50% with 1 dora. This is 75% of getting that at least 1 han. If we wish to further scrutinise into the small small details, getting a ura-dora from a sequence based hand is higher than a pung-based one. This further jacks up 75% to 80~85%. (Just a personal estimation given that a pinfu hand is around 30% of hitting 1 ura)
2. The Sanankou direction is very inflexible. Let's consider both cases as the worst case scenario. The sanankou hand might end up in Riichi nomi on shapon
machi. Where as the other case will end up in Riichi domi with
or
machi. Given a Riichi nomi hand, a good wait is crucial when your hand value is low. Otherwise you are putting yourself in a high risk of dealing in during the Riichi process (and you can't dama!)
3. Before considering Sanankou, one has to consider the eventual wait to consider its risk that it pose. Do you have a pair of honors to end up with? This hand is a no-no especially when you might end up waiting on dora-soba tiles.
4. The moment you keep the chance of Sanankou available, you are forced to keep
and
as long as possible. You will then be forced to discard dangerous tiles,
and
when your ankou is completed. Given the number of turns this game has progressed, your discarding of
and
will end up be mid 2nd row and even 3rd row of discards. Do you want this to happen? Without a proper planning of what you will be discarding as you progress nearer to tenpai will lead to blaming of luck instead of yourself. (I dealt in when I reached tenpai! It was sanankou! There's no way I should have bailed) Planning starts as early as 1st discard of your hand.
5. 7 pairs shouldn't be considered when your hands have good shapes as well and also when you have too many dora-soba tiles. Due to the difficulty nature of 7 pairs, one should add an additional shanten to it. This means, when you are 1 shanten, your actual speed is 2 shanten to 7pairs tenpai. So a 2 shanten to 7pairs tenpai is 3shanten. Rather slow when you have other faster routes. Simiarly to 4, the moment you try to balance 7pairs into this hand, you will end up with tanki
or
which then you will have to dama to switch to a better wait. When that happens, you are again,forcing yourself to discard
and
in the late game for a rather low value hand.
7 Pairs is good when you have honors tiles (even if 1 has been discarded, you can safely assume there are 2 more in the wall while you cannot assume the same for other tiles), and no dora-soba tiles (so you can still utilise dora via tanki machi)'
6.
is the worst discard ever. If you are able to kan the
, it basically rewards you a han (32fu) and your hand is in the right position to go for a speedy hand.
7. The last point is more of a general way of playing a hand and is based on a concept that aiming for a hand that do not consider utilising dora is an extremely risky play. Look at the bigger picture. Do you know there is a way to lower your chance of dealing in after Riichi? The answer is planning. Plan your hand whereby it can utilise as many dangerous tiles as possible yet have rather decent reward from it. Even if you are able to riichi on sanankou, you will fail to utilise many kinds of dangerous tiles and that is
. Your deal in rate is very high after Riichi. If you plan for
waits upon tenpai, your deal in rate will be a lot lower.
Please don't argue on how going for such a wait is lousy because "nobody will discard the dangerous tiles you are waiting on when you riichi" Because the main purpose of Riichi is never to hope for players to deal it but to paralyse them and go for self-draw win.
A good Riichi is one that gives good reward with low risk (because your hand is locked after that)
So, take this chance and get ride of
when it is safe.