MickyB, on 2012-August-28, 07:55, said:
Okay I see your point, but I'm not convinced yet.
As responder I may or may not have a 4 card M when I invite.
So when I do have a 4cM, then, presumably the auction would be the same, regardless of which method we play 1NT>>2♣ etc.
The only time when the auction will diverge should be when responder does not have a 4cM. But in these instances it is not be immediately known whether responder has a 4cM or not.
1NT>>2♣>>2D>>2N in this scenerio we reveal that opener has no 4cM, but responders hand remains unknown
1NT>>2NT in this scenerio we know that reponder has no 4cM and openers hand remain unknown.
I don't see why case 1, neccessarily makes the defence much easier.
I think I would lead "normally" against both auctions, but I do agree that after seeing dummy I would likely be better placed knowing opener has no 4cM.
Similarly,
1NT>>2C>>2M>>2NT
1NT>>2NT
The defence learns about openers 4cM but once again responers holding may still be unknown.
Anytime responder has GF values the auction should be the same regardless, so 1NT:3NT would be repeated in both scenerios.