https://www.cengage.com/resource_uploads/downloads/0534094929_46534.pdf
Regarding yesterday's bunt, the run expectancy with a runner at 2nd and nobody out is 1.19 runs. The run expectancy with a runner at 3B and 1 out is 0.98 runs. But it was the bottom of the 9th in a tie game, so that doesn't really matter. The probability of scoring at least one run with a runner at 2nd and nobody out is 0.62, and the probability of scoring at least one run with a runner at 3B and 1 out is 0.69. So McKinney getting the bunt down increased the probability of winning the game. I don't know his probability of successfully getting a sac bunt down, but with the way he's hitting, it's probably significantly higher than his odds of contributing if told to swing away.
Most of Montoyo's bunts are ******** because they've come in situations where he's decreasing his total run expectancy in order to increase his odds of scoring at least 1 run, but in yesterday's situation it was very defensible.