I'll take the Bills defense against the Titans offense over the Titans defense against the Bills offense 10 out of ten times.
If the Bills offense can sustain drives and avoid 3 and outs, letting the defense rest then McDermott can do his smoke and mirrors show to make them look better than they are... playing defenses like this one that can force the Bills into short drives allowing them to dominate time of possession really exposes the weaknesses the Bills have on defense.
A bad defense can also let the Bills get out to a lead putting the ball in the air more which plays more to the strength of the defense.
I'm not saying the Steelers or Titans are an easy out or that they aren't very good teams, but Bills match up better against them than they do the Colts.