Like I said, I mostly agree, PG (and I definitely agree that having a hitter with the balls to not swing in that situation is a major plus, not just because of THAT situation but also because he will usually be a smart and disciplined hitter in ALL situations). Just quibbling over what the percentages actually say, really.
First, I disagree that the equation is batting average on a well-located pitch (maybe .250 for a good hitter, closer to .200 for an average hitter) versus the theoretical .500 OBP on an "either way" take. It should be BABIP+ROE for that swing (higher than BA) plus the BABIP+ROE for subsequent swings after a spoiled pitch, versus the .500 OBP. And really, also the percentage chance of an obvious ball (1.000 OBP) on subsequent pitch(eS). Or, as I said in response to lefthookdad, BABIP + ROE + BB for the entire AB (not just that swing) versus the theoretical .500 OBP for the take on that one swing. The earlier in the game, and the closer the game is, the more I would like the hitter to err on the side of swinging in this situation, because there is also the additional expected runs scored for that percentage of balls that will be hit for extra bases, too. Overall, I suspect that if we were to break it down and actually do the math, the take would have to be on a pitch slightly worse than a 50-50 pitch in order to make it worth not swinging as a rule.
I also disagree that it is the hitter's judgment ALONE that should be in play. If the hitter believes a pitch in a particular location is a 50-50 pitch, but the umpire has clearly and consistently called the pitch in that location a strike,mother hitter should be swinging. I also was not talking about a "take" sign, but a sign from the coach to the hitter that the coach believes it is a 55-45 (or whatever, depending on the hitter's skillset) situation. Not a "take," just a coach highlighting a situation and reminding the player to swing wisely. I realize this isn't necessarily the player PG was talking about and wanting on his team (the guy with the smarts and balls to know this and choose this himself), but I still think it would be good practice.