The more I watch, the more I realize that the experts, the coaches, say it best. Belichick says you have to make plays. It really doesn't matter where those plays are made or who makes them as long as they are made.
Think about the Patriots Super Bowls. Both the offense and defense made the plays when they needed to make them in the first SB.
In the second, a rash of injuries (Harrison and Wilson) in the secondary, made the defense look like a sieve, and low and behold, Brady airs it out and gives one of the greatest offensive performances of all time. The offense made the plays.
In the Giants' SB, they almost made enough plays to win, but the Tyree play and the Samuel missed INT and bad offense--Patriots didn't make the plays.
It really doesn't matter IMO where those faults lie, because we have examples of both causing losses, and we have examples of the offense leading the team to victory while the defense fails, and vice versa.
Try to get the best players you can and execute.