Pretty good explanation of when you should go for two for the win.
Something else I want to add. if you're down by 14 in the second half and you score touchdown -- you should go for two point conversion.
You have basically 50/50 chance of converting it.
However, teams failing back-to-back two point conversions is dramatically less. Meaning if you don't convert the first attempt, you're likely to convert the second one.