I think you always have to go with Bears D. We're talking about a record breaking defense here. The league record of defensive touchdowns in a season is 9, I think, and the Bears already have 8 halfway through. Also, they MAKE those turnovers- they're so good at forcing fumbles, and getting sacks, blocked kicks.... Not to mention Pittsburgh is still without Polomalu. Yes, they mangled the Giants at the end of the game, but that was Eli playing poorly, not Steelers playing well.
I think you always gotta go with Bears D. At this point, benching them is like benching Arian Foster. Worse, in fact. If you look at the difference between Bears D compared to other Ds, they're averaging 5-6 points more than the 2nd best defense, which is Texas. You can't ever bench them.