Which long suit to make Trumps?

Noel Coward, who had a good sense of humor, said, "I like long walks, especially when they are taken by people who annoy me."

In bridge, we fairly often have a long suit. When you and your partner have different long suits, how should you decide which to make trumps? Look at the auction in today's deal. When East overcalled one heart, South was not strong enough to respond two diamonds, but, not wanting to pass with seven points, he compromised with one no-trump. West competed with two hearts, knowing that his side could not have game values if the opponents were honest. Now North overbid slightly with three clubs, but he wished to confirm the six-card suit. Then it could have been right for South to pass, but he knew that if each minor were a 6-1 fit, it was usually right to make the weaker hand's suit trumps. The opener's high cards will still win tricks, but to get value from the weaker hand, it needs to generate trump tricks. So, South rebid three diamonds. What happens to each minor-suit contract? Three clubs has five top losers: two spades, one diamond and two clubs. To achieve down two, East has to get a diamond or spade ruff. That is not easy to realize. Three diamonds is tougher to defeat. West must start with two rounds of trumps to kill the heart ruff on the board. At the table, after a heart lead, declarer won with dummy's ace, played a heart to the king, ruffed his last heart and played dummy's second trump. He lost only three spades and one heart.