Which Provides Better Performance?

When loading models and connecting a database, is there a "best performance" way to do these things?

1) Loading Models:

Code:

use App\Models\MyModel; + $model=new MyModel(); + $model->myMethod($data);

  = or =

Code:

$model = model('App\Models\MyModel'); + $model->myMethod($data);

2) Connecting to Database:

Code:

$db = \Config\Database::connect();

  = or =

Code:

$db = db_connect();

  = or =

Code:

$db = $this->db;