A thread like this come up every year. People were fretting about Brady's legacy before each of the last several Superbowls.. I posted this in the thread preceding the last SB.
The Brilliance of Tom Brady
If the Pats win this SB with Brady at the helm, he will have a score of 1.333. If the Pats lose this SB Brady's score will be 1.389. If, instead, the Pats lose to KC, his score will be 1.444.
Compared to Montana's score of 1.909 any of these secures Brady's legacy as the best SB era QB of them all. Btw, no other SB era QB is worth doing this exercise for. No one comes close to consistently driving his team closer to the ultimate prize than has Brady. His legacy just on aggregate success is beyond secure, it is untouchable.