[Siegmund]

This is a question that really only arises in a somewhat nonstandard system, so, for the moment, don't worry about how the auction began, just how you would place the contract.

Matchpoints. You know your partner has a balanced 15-18 type hand with exactly three spades.

♠ T8xx
♥ Jx
♦ x
♣ Q98xxx

You have a choice between setting the contract in 2♠, declared by the strong hand, or 3♣ declared by you.
Which do you pick? How much would you have to change the strength of your hand or the quality of your suits to change your answer?

Edited in light of the (unsurprising) first two answers: would 4-2-2-5 or 4-3-1-5 be just as obviously spade-preference hands, or would you still rather be in the likely 8-card minor fit?

[Fluffy]

give me the ace of clubs and I'd be in 3NT. Untill then I play 3♣

[nigel_k]

I would nearly always prefer 3♣ to 2♠ with this shape unless it was something like KQJx xx x 765432.

[han]

Definitely 3C, plus is good.

With only 5 clubs I would almost always opt for the 4-3 spade fit.

[JLOGIC]

Obviously 3C, our hand sucks for 2S.

[VM1973]

Put me down for a club suit. The problem with the spade fit is it's too likely that we'll need to ruff diamonds in hand.

Just another trolling response by yours truly.

[whereagles]

3C obvious. 2S is not matchpointitis, it's just bad bridge.