Based on the Tom Tango research, run expectancy is about 0.86 runs with man on first and one out, versus 0.66 runs with man on second and two outs.
In a case like yesterday, though, it’s not run expectancy we want to look a—that is, how many runs a team is expected to score—but run probability, meaning what are the chances a run will score, because one run is what was needed, and not many runs.
Run probability with a man on first and no out is 41.6%, while a man on second and one out, it’s 39.7%. So the chances of scoring at least one run, which is all we cared about in that moment, is actually worse after the successful bunt. Not enough worse to start firing people over, but definitely not better.
If you want to increase run probability after a sac bunt, the only situation it makes sense is with man on second with no out, which is 61.4%, to achieve man on third with one out, which is 66.0%. That is definitely better, but also, this is the only situation it even makes sense. And that’s why sac bunting has gone the way of pitchers batting—it just doesn’t make any sense outside one very specific circumstance, if what you want to do is better your chances of scoring runs, or even scoring one run.
As an aside, if Cody Stavenhagen is characterizing run expectancy as being 80% and 65% in yesterday’s case, then he is unclear on the concept, since he is confusing run expectancy with run probability.