To me rating QBs deserves a great deal of attention to situational awareness. Making plays on third/fourth down, Red zone, end of the half, and especially the fourth quarter. We've all seen the garbage time, prevent defense stats that look great in a box score. If you actually watch the game you go back and see a stinker performance got them in that position to start with.
I know W/L record has a huge team component to it, but if you really look at it, the greatest QBs impacted games and have won a lot of them.
I can't think of a position in sports that has any more to do with winning, giving somewhat adequate resources than QB....perhaps Goalies in Hockey. But, they can only keep the team in the game, eventually you need some offense to win.
For me, Stafford is a good QB, I want Allen to be great.