[mycroft]

Frequently the extra trick is the "unavoidable loser" you have when you're Ax opposite xx (or 3v3 or whatever) that you can pitch on the long card in the 5-4 after pulling trumps, and then ruff with the "fifth" trump (this tends to only work when they break 3-2). So you make 4-and-a-ruff, and 5, and the A, and enough else to make 12 tricks; whereas in the 5-4 fit, you have nowhere to pitch the loser, and you make 5-and-no-ruff, and 4, and the A, and only enough for 11.

(if your loser is in the 5-4 suit, then this works if they don't lead the scary suit, or...)

In slam, this is quite likely because you expect to have control of both suits. In game, you're less likely to have control of both suits, and that gives the opps enough time to develop and take that "unavoidable loser" before you develop and take your pitch. Frequently the 5-4 fit works better, because bad breaks or multiple losers are less likely, less damaging, and easier to control than in the 4-4 fit (even 5-3 can be more tolerant of bad breaks than 4-4).

[blackshoe]

Hm. Good point, Mycroft.