The line most likely to succeed based on mathematical probabilities.
As South, you play in 3NT. West leads the jack of spades and you win the third round with the queen. You have eight top tricks and chances in the red suits for more. If diamonds are 3-3, you can set up the suit by ducking a round.
If East has one or both heart honours, you can make an extra heart trick by using the ♦A-K as entries for finessing. With no apparent way of combining the chances, you need to choose between the two.
The chance of a 3-3 diamond break is about 36% while the chance that East holds one or both heart honours is about 75%. The percentage play is the one with the higher probability of success, in this case finessing twice in hearts.
Note that in practice you would cash some clubs before committing yourself, though as the difference in percentages is so high, it is unlikely that you would have cause to change your mind.
