[JaredL]

Isn't the selection bias that comes from teams that suck on offense/are playing a great defense being less likely to go for it than teams with good offenses/against bad defenses much more important than concerns about whether the ball is 4 feet or 1 foot from the goal line?

I would think that against a given defense, the Patriots are more likely to make it from 5 feet out than the Bills from 2 feet. Because of this we should see the Patriots going for it sometimes when the Bills wouldn't, making the 65% an overestimate.