Length vs. Strength

In Friday afternoon's STaC pairs game, I picked up this hand:

S J8
H T7642
D AKQ4
C T8

I dealt and passed. LHO passed. Partner opened 2 clubs. RHO passed. I bid 2 diamonds, which showed some values (2 hearts would have showed a really bad hand). LHO passed, partner bid 3 clubs and RHO passed. What do you bid?

My first thought was to show the 5-card heart suit by bidding 3 hearts. But then I thought some more. What is partner likely to hold, and how can my bidding help him? What do I know about this hand vs. what does partner know? Which one of us can best place the contract? Even if we have a heart fit, do we want to play in hearts?

Partner is showing a big hand with a club suit. He has nothing much in diamonds, so he has to have points in the majors. Even if he has 3 good hearts, say AQx, we may have one or two heart losers in a heart contract. Plus, if we play it in hearts, I will have to declare so the opening lead will come through partner. All things considered, I thought that any contract should be played by partner, and that the most likely contracts for us would be 6 no-trump or 6 hearts. So I decided to bid 3 diamonds. My plan was to bid 6 no-trump if partner bid the expected 3 no-trump, or 6 hearts if partner bid 3 hearts.

Partner duly bid 3 no-trump which I raised to 6 no-trump. This got us a cold top on the board, since the entire hand was as follows:

S J8
H T7642
D AKQ4
C T8

S T754........ S K962
H K3........... H QJ965
D JT932..... D 75
C 97............ C 65

S AQ3
H A
D 86
C AKQJ432

6 no-trump made 7. West led the Jack of diamonds. Partner won the ace and ran the clubs. East had to guess whether declarer had the AQ of spades, in which he had to hold spades and discard hearts, or AKx of hearts and Ax of spades, in which case he had to hold hearts and pitch spades. He eventually threw spades so we had an easy 13 tricks. The most popular contract was 6 clubs.

Note that even if partner's majors were reversed, the best contract is still 6 no-trump. But if he had that hand, if I had bid 3 hearts we would have gotten to an inferior 6 heart contract.