I was referring to bagging an unconscious patient. It seemed like from the original posters question they were referring to npa vs. opa in these types of patients. Obviously there are better methods to secure an airway, but when it comes to basics there is no better option.
If you don't think every patient that you are bagging requires an OPA you might need to go back to EMT-basic school. That is the most basic skill, and can make a different between a adequate and inadequate ventilation.
I just recently read a great review of how to pass the NREMT paramedic exam. Here is the link, it was written by a guy who passed the NREMT so it's probably pretty credible. http://passmedics.com/about-the-nremt-paramedic-exam
always OPA unless a suspected skull fractuce. OPA is a vital piece of equipment to be able to secure the airway and not allow the tongue to occlude it.