Superior coaching and great talent evaluators, particularly on the defensive side of the ball. Insane how they keep losing offensive coordinators yet their offense gets better each time. From Cameron to Caldwell to Kubiak. Not to mention, they've had Pagano, Rex Ryan, Hue Jackson, and Greg Mattison as DCs over the last 8 years. To me, it looks like both the Ravens and Pats run systems with specific roles that are very, very well defined. The cohesion at the top (Harbaugh and BB) allows the personnel managers to acquire players suited for those specific roles. For the Ravens, that approach looks more obvious (at least to me) on the defensive side of the ball. Moreover, both teams seem more concerned with quality depth on offense as opposed to superstars who eat up the majority of their cap. I'm not suggesting that you can't win with superstar WR's and RB's and highly paid OL's, but neither Brady or Flacco are surrounded by any, except maybe Gronk.