No Advantage Here to the Balanced Suit as Trump

Q 6 2
A 7 4 3
Q 10 6
A K 2
J 9 8 7 K 5 4 3
K J 8 10 9
3 8 2
J 10 9 7 4 Q 8 6 5 3
A 10
Q 6 5 2
A K J 9 7 5 4
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This interesting hand appeared in Frank Stewart's column, and just to keep our feet planted on solid ground, I thought it might behoove me to give a hand where the balanced suit doesn't work best (nor the major, for that matter). Six hearts has no chance here. Six diamonds is makable, though Stewart refers to a declarer who didn't make it, placing his hopes on an onsides king of spades.
I have said elsewhere that by and large when a suit is balanced, you'll probably have the same losers whether it's trump or not and that you won't lose the value of top tricks in a suit by not naming it trump. This, as I have emphasized with "by and large" in italics, is not an absolute rule, for indeed, I then went on to say that this won't necessarily be true if you have a stopper in your (relatively) weak balanced suit and a third suit on which you can get sluffs. Here the third suit is clubs, of course, with two top winners.
As Stewart pointed out, the way to make six diamonds is to take one round of trump with an honor from the closed hand, go to the ace of hearts, sluff two hearts on the top clubs, and lose a heart. Now on regaining the lead, you enter dummy with a trump honor and ruff the third round of hearts, and on the remaining heart, sluff the spade loser.
No argument. Certainly six diamonds is a much better contract on these cards and I have never tried to obscure the fact that the balanced suit won't always work best. Nevertheless, I do want to make a few comments to put this hand in some perspective. I'll start by saying I wouldn't be ashamed to be in six hearts here. No one's going to get 'em all right. You can't see your partner's cards before dummy comes down, and though you'll have some idea of your partner's strength and distribution before that momentous event (dummy coming down), there's no way of placing honors exactly, and people who say they know exactly what their partner will have are talking nonsense. Just in the past week, as I first write this, I told a novice I'm shepherding that to me that's one of the most exciting times in bridge, when dummy comes down and you see the firepower you're going to have to work with.
Now here, if the king of clubs were the king of hearts, six hearts would be a cakewalk -- even on a 4-1 heart split. No, the smart-ass reply that if frogs had wings they could fly wouldn't faze me here. I've already acknowledged that the unbalanced suit works far better here. But I'm now looking at the long-range view and pointing out that you can lose a lot of points going for the strong minor over an adequate major, or going for a strong unbalanced suit over an adequate balanced, and if the heart suit wasn't "adequate" here, well, there'll be pul-lenty of times on a 4-4 fit it will be.
I might make an even less dramatic change in the hand to make hearts work better than diamonds: put the king of hearts in East's hand! It must surely be annoying to the defense to have 5 of the top 7 cards in a suit and get just one trick out of that, but such is the way of the cards. Or the jack of hearts with declarer, an awfully difficult card to locate on the bidding, would seem to have done the trick.
I think I'd have more hope for a pair of novices who wound up in six hearts than those in six diamonds because the suit looked so strong. Stewart gave North the opening bid of a club. With the popularity of 15-17 pt no trump openings, it's not clear why North didn't open a no trump, making the locating of a 4-4 heart fit near inevitable, but in any event, though we take note that the balanced suit won't necessarily work best, this hand is a bit of a freak: everything is just so: the club honors, the weakness in hearts with the king in the wrong hand, hearts 3-2, the spade loser that the opposition can't set up on opening lead, in which case you couldn't make slam in either suit. Did this hand ever exist? Or was it devised? Looks hokey to me.
Ultimately the choice is up to you, and I've always advocated that you make yourself your own expert by watching hands very closely.