How about the reverse effect, which we also saw come into play in Sunday?
Atlanta had a 2 score lead and played conservatively. Do you think Dallas is getting a stop when Atlanta knows it's only a 1 score game? Yeah, I don't think so
Yep, that too is a factor. I'm not sure Atlanta would have played much differently though because if the Cowboys would have kicked the XP Atlanta would still likely have been very conservative knowing that the only way they could lose in regulation would be if they got careless, and knowing it would still have taken a TD and 2 pt. conversion for Dallas to even tie.
And there are other factors. For example, there is more pressure when the conversion is for the tie than when it is to get within 7 and still needing another TD. Not sure who that favors, but my guess is it favors the offense because the offense will know the play it is running and the defense might start guessing in an effort to stop the conversion and find themselves out of position.
Then there is also the possibility that had we kicked the XP the first time we still may have scored the 2nd time quickly enough to allow for an onside kick, or at least to get to overtime, which provides a better chance of winning than relying on an onside kick, especially under current rules.
All I'm saying is that there aren't easy and simple mathematics because there are a number of factors, some of which can't be easily quantified.
And ultimately, their are arguments for either approach. In this case it worked because the onside kick worked, but the onside kick has a very low odds of working, especially under current rules.