I am not sure (at all) that Jimmy G is better. I am certain that Brissett isn't. Obviously the situation impacts it but if you said (all things being equal) the Pats could have either Brissett or Tyrod on their roster the answer is Tyrod (and it isn't even close). Everyone loves a QB until he has to play.
I'm not trying to repeat things but on a per attempt basis he is right in the middle of the league and top 10 in terms of TDs and fewest INTs. We will see the attempts go up and the gross numbers go up. If you want to see what it all equals it is in the Mike Williams thread.
The Patriots don't care about a player's value to your team. They care about how the player fits in THEIR offense.