Quick suit combinations: the answer

Here was the question again.

How do you play the following suit at matchpoints?

Dummy

A Q 10 8

Hand

4 3 2

Which very similar line actually achieves a higher expected number of tricks?

And now for what I think is the answer (with the help of the nifty program "suitplay"):

I'll call the best two lines A and B. Both Lines A and B play initially to the eight, and repeat any marked finesses on the second round if the eight loses to an honour. The hands where they differ are when the eight loses to the nine. Note that Line A plays to the Ten next, while Line B plays to the Queen next, Line A being the dominant line as far as beating all other lines.

The table below presents the number of tricks won by Lines A and B after the eight loses to the nine on the first round.

West	East	Percentage		Line A: To 8, then to Ten then Ace	Line B: To 8, then to Queen then Ace	A beats B	Trick Difference
KJxx	9x	4.8%	Tricks	3	2	✔	+1x4.8% = 4.8%
KJxxx	9	1.2%	Tricks	3	2	✔	+1x1.2% = 1.2%
Kxxx	J9	1.6%	Tricks	1	3		-2x1.6% = -3.2%
Kxx	J9x	5.3%	Tricks	2	3		-1x5.3% = -5.3%
Jxxx	K9	1.6%	Tricks	2	1	✔	+1*1.6% = 1.6%

Line B, however, wins more tricks on average, slightly, because of the two-trick gains when the Jack is offside and the King onside to at least three.