The Seattle Seahawks and the San Francisco 49ers act like the N.F.L.’s fiercest rivals, which might seem strange for teams that have never met in the playoffs. Stranger still, the tension’s origins trace to five years ago, when both teams were bad and their current coaches led college programs.

At midfield after one meeting of those college teams, the coaches asked each other a question that endures as a perfect volley for the current state of debate.

“What’s your deal?” one shouted.

“What’s your deal?” the other replied.

The Seahawks and the 49ers play for the N.F.C. championship on Sunday, the winner advancing to the Super Bowl. For those in and around Seattle and San Francisco, it is the latest talking point in a long-running debate over superiority.

Seattle and San Francisco are like rain and fog — seemingly different, but mostly made of the same stuff. The cities and the suburbs have been competitors for decades, once battling for supremacy as shipping ports, railroad destinations and jumpoff points for gold seekers, more recently in industry and technology.