provider.ts

// When using a provider to call AngularFire2
// which syntax do you use the most

// Provider
getItems(): FirebaseListObservable<any> {
  return afDatabase.list('/items');
}

// Inside the class do you:
  this.items = providerName.getItems();

// Or do you
  providerName.getItems.subscribe( itemSnap => {
    this.items = itemSnap;
  })