I'm not old enough (21) to have seen any of the four play live, but I do have a fairly strong, related opinion so I'll post it and you ignore it if you want.
I don't believe in the clutch QB. Further, I've never seen any evidence of 'choking' that couldn't be chalked up to other factors just as easily, so I have no reason to believe in that, either.
Who was the best quarterback to have when the chips were down? The same guy who was the best no matter what the game situation was, Roger Staubach. Who has the most come from behind wins? Brett Favre, the same guy who has the most total wins. Who'd he pass for the 4Q comeback title? John Elway, the same guy he passed for the wins total. Doesn't that make anyone else suspicious at all?
You can say players like Tarkenton and Marino and Moon choked in the playoffs, but when was either ever on a team that should have won a Super Bowl? Tarkenton's Vikings weren't as good as any of the teams they faced in his three appearances. Marino never had the best team entering the tournament. Moon had a couple of teams that should have been AFC champions, sure, but he put up 38 points in one of the losses and was outdueled by Joe Montana in the other - and since they'd have been going up against the Triplets in those Super Bowls, he wouldn't have gotten a ring out of it anyway.
I don't consider living up to expectations but failing to exceed them to be choking.
KJJ, I also think you're underrating Meredith and Perkins. In the context of his era, Meredith had good solid numbers equivalent to White or Morton in theirs. Perkins name came up quite a bit around me, and not from Cowboys fans, as a guy 'more deserving than Floyd Little for the Hall of Fame' so I don't think it's fair to say he gets no consideration.