Posted 2012-April-04, 09:36
I don't normally comment in this forum, but I thought I would add my 2 cents worth.
The original idea of inviting slam with 4NT if partner rebids 1NT is fine, as far as it goes. One of the posters even went so far as to mention that the only possible contracts would be 4NT or 6NT. And for the purposes of this Forum, perhaps that is as far as we should go. The main point is that a balanced 19 count opposite an opening bid is not a slam force - it is a slam invitation.
However, if one goes back to the initial post, one can see the spoiler. It was mentioned that the at the table result was a "good" 6NT which was made. All well and good, but 6NT is only a fair contract. You start with 4 clubs, 3 diamonds, 2 hearts and a spade for 10 tricks. There are many possibilities for an 11th trick (spade finesse, diamond finesse or drop, various plays in the heart suit that can result in an extra trick, and other possibilities beyond the scope of this forum), and, once one of them comes in, there are some possibilities for a 12th trick. Also, the opening lead may give you an 11th trick, which gives you many more chances to work on making a 12th trick. All in all, I would say that 6NT is a reasonable contract.
However, the BEST contract is 6♣. It needs far less to go right in order to make. And 6♣ is a contract that is very difficult to reach for any players at any level. While 6♣ does not score as well as 6NT, it is much more likely to succeed. So, even at matchpoints, I would rather be in 6♣ than 6NT.
EDIT: I note that in one of the early posts nigel_k mentioned that 6♣ is the best contract on this hand.