On talent, there is no doubt who the best Bills QB is: it is clearly Josh Allen. He has that IT! factor. It's must-see TV when he is on the field.
Peterman has looked good -- very good -- in the preseason. But there is no doubt who is more dynamic and who has more upside between him and Allen. So now with McCarron is out of the picture, all things considered, I would roll the dice with Allen.
Also, consider this, as far as game experience, Peterman has exactly two NFL starts, and both of those were about a quarter. He has one half of a game more playing time than Josh Allen. Yes, he has a head start on practice and study time, but at the end of the day, it is a meritocracy and the better player needs to be on the field.
Start Josh Allen now!