3
♣ for me, for the reasons that Ken set out, even without specialized agreements.
Nothing matters, really, unless partner has slam ambitions, and, then, everything matters
The splinter makes it impossible for opener to evaluate his round suit holdings, while preventing us from showing our source of tricks, and our lack of anything better than 5th round heart control.
After 1
♠ 3
♣, partner will correctly play us for 9+ black cards, and about this sort of strength in the blacks, and no meaningful high cards in the reds.. but we can still have and often will have a stiff (a void is always much less common).
So with AQxxxx x Axx Kxx, he can drive to slam, comfortably. With AQxxx Ax xxx Kxx, he can bid 3
♥, and now our 4
♦ call will get us to slam, and so on.
I think the main points are:
1. for slam purposes, the club suit is often going to be critical as a source of tricks.. and the splinter leaves that out
2. For slam purposes, the fit-jump shows the source of tricks and will often allow us to show the diamond shortness anyway.. we may even get to show the void, by cue-bidding 4
♦ over 3
♥ and then 5
♦ over 5
♣
So the splinter consumes valuable bidding space while leaving half our story untold. The fit jump consumes less space and offers the possibility of telling all or almost all of our story.
'one of the great markers of the advance of human kindness is the howls you will hear from the Men of God' Johann Hari
(P)-P-(P)-1♠,
(P)-?