I see three strategies:
A) Make the kan right now, be tenpai on 3456m 2345s, and end with riichi only (+dora?).
pro: have an extra draw.
con: potentially gives some dora to your opponents, while you're still not tenpai.
B) Throw away the kan, be tenpai on 3456m 2345s, and have a chance to get pinfu (by using the 1m for the pair).
pro: one more yaku, granted ryanmen wait (fastest hand).
con: no dora.
C) Wait to be tenpai to declare the kan, break one of the ryanmen now (I'll discard 3s in this case), be tenpai on 36m 4s, and end with riichi only (+dora?).
pro: chance for rinshan kaihou.
con: slower the hand.
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My choice: B) Discard
If we get pinfu, we can also stay in silent tenpai and hope to switch some shuntsu to get sanshoku.
With options A and C the hand will worth nothing without dora, and I don't like to rely on hypothetical dora.
