Diamonds are (often) a Girl's Best Friend


J 10 8 6 3
10 8 2
A J 10 9 4
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7 5 2 K 4
Q J 7 A 9 6 4
6 5 3
A K 8 7 2 Q J 10 9 6 4
A Q 9
K 5 3 Contract: 4 spds, 5 dia, 6 dia
K Q 8 7 2 Vul: No one
5 3 Opening lead: A of clubs

Here we have consideration of the major over the minor and of a balanced suit for trump vs. an unbalanced, not to mention bidding a slam-dunk hand, along with The Law of Total Tricks.
There's nothing very tricky about the play in either direction, so I will content myself with noting what can be made (and why). You will note that slam is possible in diamonds though not in spades because of the value of the unbalanced suit as a side suit. A few days ago when I said that if push came to shove on an unbalanced major vs a balanced minor, I said I'd go with the major which will steer you right a lot more often than the balanced over the unbalanced. I should have said I'd go with the major on game bids, figuring that there may be no difference in the tricks taken in the two suits, and if there is a difference of one, the 4 level in a major still pays off better than the 5 level in a minor. But slam bids are something else again. There you need the same number of tricks for the slam bonus, and I'd have a strong inclination to opt for a balanced minor over the unbalanced major. I may be wrong, but then, I may be right, also.
Here, if you're not slambound, and it's understandable why one would not be, then the adequate 8-card spade suit has to be preferable to the 10-card diamond. (No one bid slam here, a little surprisingly. But if the spade hook is off, you can't even make game in diamonds, though you can in spades, so it's not a terribly robust hand, by any means. The club void in the weaker hand makes for the slam, along with the onsides king of spades, but it's difficult for that hand to envision slam opposite a partner making minimum bids.) You can make 420 in five diamonds with an overtrick, 450 in 4 spades with an overtrick.
Another feature of the hand is the superfit in each direction. Ten diamonds with the stronger fellows, 11 clubs with the weaker, no one vul. With a superfit, i.e., one where both pairs are strong enough to enter the bidding, I advocate a strong propensity to push on, often not knowing who's bidding to make, who to sac, including yourself, but you gain a tremendous advantage in trick-taking potential if you are able to name the trump suit. With a sprinkling of top honors, you can often make the game level worth pursuing, maybe higher.
Here the club bidders did well not to mess with those in four diamonds, missing their game, missing their slam indeed. But a club sac over 4 spades would pay off as would 5 spades over 5 clubs, as would 6 diamonds over an unwise 6 club one-too-many sac over a 5 bid but not one-too many if the opposition doubles that in preference to 6 diamonds, and then 7 clubs over 6 diamonds. So it does get touch-and-go up at the 5 and 6 level. You don't know who has already bid "one too many" and you don't want to be that guy. But I would certainly think the N-S pair would want to push to game on that superfit.
Both pairs seem to have been a little off base here. Four diamonds, being neither a jump nor a new suit, can't be forcing. If you've found a spade fit and bid on the four level, surely you want to bid game -- with a 5-card spade suit, no less, that your partner can't be sure about. But South too, with a partner not willing to let the opps take the hand and now with knowledge of a superfit (after all, North can't know South has 5 diamonds at this point, but South can know North does), surely should have pressed on. Since it sounds like North's once-bid spades are only four pieces long, a later diamond bid seems to be looking for a better fit. So I certainly wouldn't blame South for saying 5 diamonds, which isn't as good as 4 spades. Who knows? North might even bid slam.
[Years later: Yes, I'm writing as if the bidding sequences were available, and don't know what I was thinking. I suppose I was looking at several bidding sequences on paper and simply neglected to put them with the hand. Still, I believe the points being made are understandable and valid.]
Lastly, there was one bottom-feeding pair that found their slam-dunk club fit on a 3 club bid by one partner, 5 clubs by the other, and with a chance to pass out 5 diamonds for an average board, went to 5 hearts! This was bid by the West hand above, the first reference to hearts, though his partner had made an early takeout double before raising 3 clubs to 5. Hey, undertricks cost as much in a major as in a minor, no difference, and especially when you've found a fit do you not want to mess with your fit. Five clubs (down 2)would have been a good sac over 4 spades. Six clubs over 5 diamonds would have been "one too many" over five diamonds, and disastrous if they pushed the opps to six diamonds, but at least it's not a completely haywire bid. Five hearts is just completely out of the ballpark. Minus 1700.
The slam-dunk advocacy is closely related to The Law of Total Tricks. If each side has a superfit, then there may be enough tricks for each to be bidding at the four or five level with impunity. I say "impunity", which would include making a good sac, not that each side can necessarily make at that level. And you'll probably want to push to that level, unless you are facing unfavorable vulnerabilty and are not bidding to make. Vulnerable undertricks (doubled) get expensive in a hurry, so I would strongly advise against inviting them against non-vul opps. It may turn out they can't make their bid either. To read each side's potential so closely that you can judge you'll only go down one, and they can make game is not such an easy business. Against slam, down four would be "one too many".
Anyway, when one side has a 10-card fit and the other an 11, then the Law of Total Tricks says there should be 21 tricks between them. And what do we find? The clubbers can make 9 tricks, and the other side 12! Bingo. But that's 12 in diamonds, not in spades. So the stronger side wants to push on past the weaker's sac up to a point, which here would be 7 clubs. There you would have to relinquish your trump suit and double. And the weaker? At that vulnerability, 5 clubs is their max if the opponents don't go to the diamond slam, and 7 clubs would work if they do. (Six clubs would be worth it if the opps were vul.) You can't know all this during the bidding, but it's worth noting your opportunities for future reference.