It depends on the scoring system I think. If it's 6 points for a touchdown I tend to lean toward Stafford, 4 pts I lead toward Cam. That would've been a 40 point swing a year ago.
Also I think Stafford has the best chance to repeat his 2011 performance. Best/Leshoure and probably Kevin Smith before long all on the shelf. A defense with 0 talent at the cornerback position, then they cut Berry to give them negative talent. Titus Young looking unstoppable in camp. Finally drafted a LT early in the draft. It all means Stafford is going to be near the top in pass attempts again this season. Also added Ryan Broyles in the 2nd round at WR for good measure. Only real drawback I see is Megatron is madden cursed...if you believe in that kind of thing.
Cam's rushing scores were so out of this world it's almost certain he'll face a regression to the mean. Teams will gameplan better against him there. Added another goalline vulture in Mike Tolbert to protect the QB. Gave Cam no new weapons in the passing game to help Steve Smith. Just paid Stewart a big contract, they will run run run. Defense should be a lot better. Also Cam's passing numbers faded badly the 2nd half of the season, after two 400 yard games and a 375 yard game to start the year, he came back down to earth and late in the year he couldn't hookup with Steve Smith the way he was earlier.
Still, Cam Newton was only a rookie so his upside is still majorly off the charts, especially with his ability to run. Still, you gotta think 14 scores and 706 rushing is his ceiling and Stafford still outscored him in 6 pt/TD leagues. You also face a bigger injury risk with a running QB.