[mikegill]

I think both 4 and 5 spades are reasonable bids, and that neither would ever be called "clearly wrong". Here are some points I'm not sure have been mentioned.

1) Let's think about what partner is likely to have. He is a passed hand, which probably will average something like 8 HCP, especially given that RHO showed 16+. How many defensive tricks do we think partner will average with his 8 HCP, especially given that he's under the 1C bidder, and that all of his Qs will likely be picked up if there's a guess? I'm betting he'll take 1.5 tricks (or less) on average. I will almost never take a trick if they bid in hearts (which seems most likely since I have fewest of them), and probably around 1 trick on averave in a minor, depending on who declares. Overall our total number of defensive tricks will be 1-2, and rarely outside of that range. It seems like on a normal day they will make 5 or 6 of whatever they bid.

2) How many offensive tricks is partner likely to have? Well probably not as many, since only certainly cards are worth something to me. My extra shape means that more cards could be useful (like maybe the QJ of clubs), but still I think partner will give us a trick at best on average. (We estimated 1.5 tricks on defense, and, as a quick approximation, all of his heart honors are wasted on offense, which is 1/3 of the possible honors, so he should take about 2/3 as many tricks on offense as defense. I know the actual total will be less than this because of defensive tricks with Js and Ts in their suits). So our expected total number of tricks is 8, assuming nothing completely outlandish happens in spades.

3) Will partner bid 5S over their 5-level bid necessarily if it's right? A scenario where they're making only 5 and we're down 2 or 3 in 5S is very possible given the above information, and especially at matchpoints it's important to compete to this level. The question is would partner raise to 5S on a hand like xx xxx Axx KQxxx? Would the same people who bid 4S on this hand bid 4S on the same hand with one fewer spade, in which case partner would be wary of raising on only 2? A lot of people would preempt 4S over a strong club on KQJTxxx xx x xxx or the like. I guess this is more of a style issue - is it more valuable to preempt aggressively and advance conservatively, or vice versa. I don't think anyone has a definitive answer to this question.

4) Are the people who bid only 4S planning to bid 5S on their own? General strategy says to compete to the level where you don't know what it's right for them to do. Here, you can be pretty sure they should be bidding at the 5-level from our previous analysis, and that you won't go for too much in 5S. This argues for bidding 5S. However, they may not know they should compete, and may stop to double you in 4, which would make 5S kind of silly. It is also a valid tactic to bid 4 planning to bid 5 as long as you already know you're going to do it - however, this tactic is usually applied to lower-level bidding where you don't risk pushing them into a making slam. This method may be especially valid if you are known to be an aggressive preemptor. If you would make this preempt on one fewer spade, then they are more likely to double you in 4 for fear that they can't make anything. Especially given that they will have no idea as to the degree of their fit. I really don't have any idea what the odds are that they double us in 4S vs. 5S, and I suspect it varies considerably depending on the opponents and their opinion of you.

Overall, I think that 5S is probably a better IMP bid. It seems to win bigger when it wins. If they get doubled in 4S at the other table, you're only losing 200 likely (300 at the outside). The extra level of preemption could do nasty things to them, all of which could easily gain us 13+ IMPs. I can be wrong twice at 5 IMPs a piece as long as I win 13 once. It seems unlikely that both 4S and 5x are going down, and that's where this bid really loses. In addition to this, people seem to overbid, or to think they're being talked out of a slam at favorable. Maybe this is not true with really good opponents.

As a side note, the problem with hands like this, though, is that they're so rare that it's very difficult for any person to get a sense of what's right because they have so few data points to work with. Even in a lifetime of playing, there's always the chance that your few hands you've seen are skewed from reality to make being aggressive or conservative seem right to you.

[Free]

I don't see a reason to bid 5♠. 4♠ is good enough, but I'm considering 4♥ or 5♥.