One of my multi instructors many years ago said this... If you were sat as a passenger in a B737 and the pilot announced "One of our two engines has failed, but we are still going to take off - because we still had one good engine", you would be wanting to get off that aircraft.
My wife knows nothing about piston v turbine v twin v single reliability, but she does know if one engine fails another working one is handy. In a PC12 v B200GT scenario - she wants the B200GT - regardless of extra costs.