With DF, what "if" is not needed, because we already "know", from his time in Buffalo and San Diego. When push comes to shove, during that "must have game" Flutie may show, but odds say he will not. You can "lust" over DF all you want, and pin the Miami loss on Moulds, or be like the other Flakes and blame Andre, but DF did turn the ball over 3-4 times in that game, the last one doing the very thing all his supporters claimed he did not do. DF took a sack. In the process of that sack, DF fumbled the ball, and the game away.
DF comes up big in the small games, but comes up small in the big games (no pun intended). We already have a QB like that here now. His name is Drew.
Furthermore, the fact you even mentioned the scenario of choosing RJ or DF, as though these were the Bills only options, only proves the only way you can justify the greatness of DF is to compare him RJ. Try comparing DF to another QB, like Garcia or Holcombe (sp?).