You have to take into account the era. Montana played when it was open season on QB's and had to stand in there and take true beatings. Today, you can hit high, cant hit low, cant hit after they throw it. So Brady has had way more bites at the apple because you can be way healthier these days. Having said all that, Brady has played in 8 SB's, like 12 AFC championship games, has a winning percentage way better than Montana or anyone ever. His stats stand out above others across the board. I think you can argue Montana over Brady but for it is also valid (probably more so) to argue Brady over Montana. The 28-3 game last year is totally unprecedented in a SB.
yet here we are talking about Montana, what has he done lately?