When wiring a switch, should I break the neutral or power wire?
There was a time when switching the neutral was a common practice, but it was way more than 40 years ago.  It's no longer permitted:  


  NEC 404.2(B) Grounded Conductors. Switches or circuit breakers
  shall not disconnect the grounded conductor of a circuit.  


(In the case of your home, and in most cases, the neutral is grounded so the neutral wire is the grounded conductor.)  

This way when receptacles, light switches, etc. are switched off, they do not carry any voltage to ground, making them safer for light bulb changing, etc.