Barring an injury to Brady or a complete collapse of the Patriots around him, the Bills cannot be a favorite going into either game against the Pats this year. There's just too much history of failure against them for anyone to expect the Bills to beat the Pats.
For instance, in their first meeting in 2019, even if the Bills come into the game 3-0 and the Pats are, say, 1-2, the Bills will not be favored.