Read Also: 3rd and 5th leads By Bob Crosby
Source:
Many many years ago Eddie Kantar wrote an article on Bridge World about the advantages of fourth best leads. He provided plenty of examples where fourth best was clearly an advantage over third and fifth. After this article some players started to play fourth best because it was obviously better.
The next month Mr Kantar wrote another article explaining why third and fifth were better. Again he provided several examples where it was clear that third and fifth leads were a big gain over fourth best.
I think it can’t be clearer than this.
3rd and 5th leads clarify suit length earlier. That is a big deal when defending suit contracts, where the priority is knowing how many tricks will cash in a suit in the first couple of rounds. 3rd and low is so much more effective that few experts use old-fashioned 4th best leads against suit contracts (although some do use alternatives to 3rd and low).
Against NT, the superior treatment is ambiguous. The defensive focus is on establishing a long suit, rather than on cashing a trick or two and then switching. This makes immediate knowledge of the exact length of opener’s suit at trick 1 less important. If 3rd hand could only know one thing about opening leader’s suit, he would rather know how strong it is. Consequently, many experts use 4th best leads which allow application of the rule of 11, a tool for identifying suit strength. Others prefer attitude leads which are ambiguous about length but arguably say more about suit quality.
I will be very interested to read the other answers looking for a technical reason, because, sadly, I think much of the benefit accrues when declarer doesn’t realize 3rd/5th are being led, whereas the defenders do…
