Wow!

8 3
J 3
K Q J 8 7 5 2
A 10
7 10 9 5 2
A 9 8 5 4 2 10
------ 10 9 6 4 3
J 8 7 5 4 3 9 6 2
A K Q J 6 4
K Q 7 6Contract: 6 spades, dbld
A
K QOpening lead: A hearts

West followed his A of hearts with the deuce, giving his partner a ruff and got a diamond back, which he was able to ruff. Now another heart was ruffed in dummy, but overruffed by East, and now the fun was over. On a second diamond from East, declarer ruffed with the A and was soon on claim. Down 3, doubled.
This is the most extreme example I'm likely to find of the advantage of no trump when all suits are solidly stopped with high cards. A crossruff for four quick tricks! But it happened, and the possibility of a quick ruff was one of the disadvantages of a suit slam referred to in the discussion, i. e., when you've got a powerful supply of high cards. 'Nuff said?
And the funny thing is, I didn't recognize why I'd saved this hand for a few moments. Lemme see (I said to myself), did declarer spend the lone entry to dummy before unblocking diamonds? Did he bank on diamonds running after losing entries back to the closed hand? No, on both counts. And then I finally saw the light when I went over the hand trick-by-trick and saw that they weren't in no trump.
There's a secondary issue here, namely East's double. Well, yeah, it worked out for plus 800 instead of 300. But had declarer run to 6 no, that would've been one of the most expensive doubles East ever made, climbing toward 2000 total points in foolishness.
Experienced players frown on doubles of slams. The presumption here is that the opponents have had so much room to explore for their potential, that even if you're right (and if we are presuming reasonably competent opponents), you'll probably pick up only an extra 50 or 100 points on a down one over a non-double. And further, they may know something you don't know, such as a void or other shortages where you'd hardly expect it.
This disinclination to double slams led to the Lightner Double, which a double (of a slam) by the partner of the opening leader, asking him to lead dummy's first bid suit. Some will "correct" that to "unusual lead", but for the sake of skirting ambiguity, I'll leave it at "dummy's first bid suit".
I have elsewhere referred to a case where I was almost a victim of such an incautious double. My partner, a fairly good player, sitting on declarer's left, doubled 6 spades, holding Q J 10 low in the suit, on a rare 4-0 split on their 9-card fit. Except that declarer, also a pretty good player ran to 6 no. Now declarer led a singleton heart to A K Q 10 low low, paused as I held my breath, and finally went up with the A and thus was unable to pick up my incautious partner's thrice-guarded J.
It was several years before I realized that this usually competent declarer had a squeeze without risk against my partner. I believe I've parked it somewhere, but I don't remember the number now. Anyway, East was awfully lucky here.