This isn't a Belichick vs. Brady argument, not even close. However, it is a fun question given that Harbaugh, the rookie head coach, and Flacco, the newbie starter, were blank slates when the season began.
But I'll pick Flacco as the guy who made the difference this season - with a tip of the helmet to offensive coordinator Cam Cameron.
No question, Harbaugh set the table. His disciplined, meticulous approach made a world of difference in the way the team prepared. But unless you're Bill Belichick, the quarterback is still the man with his hands on the wheel and his foot on the gas. (Even super genius Duane Charles Parcells couldn't win in New York with Scott Brunner.)
Flacco did not run the Ravens into a ditch. Instead, the quarterback got better as the season inched toward December. When the Ravens needed to win Sunday to make the playoffs, he put it all together, leading three long scoring drives and passing for 297 yards.
Yes, Flacco has thrown too many interceptions, 12 against 14 touchdown tosses. But he stays cool, doesn't throw (or fumble) away the game, doesn't try to do more than he's capable of. He has won AFC Offensive Player of the Week, NFL Rookie of the Week and NFL Offensive Rookie of the Month. And he's tough - just ask Washington Redskins middle linebacker London Fletcher.
Flacco's statistics compare favorably to Tom Brady's 2001 numbers - his first full season as a starter. That means that after years of "Your Name Here" as quarterback (Stoney Case, Elvis Grbac, Tony Banks, come on down), the Ravens finally might have the man to lead them for years to come.