Depends on circumstance, in my view.
For normal T&Gs I teach configure 1st, assess the runway dist. remaining then either stop or add power. You wouldn't take-off normally with trim/flap/spoilers set incorrectly so I believe it's generally better to teach the same for normal T&Gs.
By 'normal' I mean a RWY of sufficient length for this operation
For go-rounds based on recovering from a mis-handled landing, then I teach full power 1st then reconfigure.