What makes the Predators so much better than the Flames?

In the playoffs this year, the difference is that Nashville is getting better goaltending, and better team defense. Their defense is limiting the number of shots their goalie has to face, and the goalie is stopping most of what he has to face. In their series against Chicago, they only allowed 3 goals against. Nashville are also getting more offensive production from their defensemen.

Goaltending (Rinne has a .942 SPCT, while CGY's Elliott was awful at .880) for starters. Even though Calgary was close to even in shot attempts at 5v5 when your goaltending is that bad it's hard to make up for it. Nashville is slightly better.

In terms of HDSPCT (high danger SPCT) Rinne is dominant, Elliott was plain bad.

Predators have the best D in the league, a better goalie and better offense

Players playing at their optimum, team playing together, and great goaltending.

The defense period. They are scoring goals to which makes them twice as hard to beat.