Vinatieri has a career average field goal completion of around 84%.
Vinatieri played 6 seasons with Tom Brady. Of those 6, he posted completion percentages below his average during 4, including one as low as 73%. Of those 6 seasons, he had 3 in which he kicked 100% on extra points.
Since leaving New England, he has played 13 seasons. In those, he has only had 4 seasons below his average, and only one below the 78% mark. Of those 13 seasons, he had 8 in which he kicked a perfect 100% on PATs, including a stretch of 5 seasons in a row - that's a remarkable 196 PATs without a miss - without Brady.
He has been consistently great throughout his career, but it would seem he has been better in Indianapolis than he was in New England.